6 Embedded PL/SQL
This chapter shows you how to improve performance by embedding PL/SQL transaction processing blocks in your program. This chapter has the following sections:
Embedding PL/SQL
Pro*COBOL treats a PL/SQL block like a single embedded SQL statement. You can place a PL/SQL block anywhere in a host program that you can place a SQL statement.
To embed a PL/SQL block in your host program, declare the variables to be shared with PL/SQL and bracket the PL/SQL block with the EXEC SQL EXECUTE and END-EXEC keywords.
Host Variables
Inside a PL/SQL block, host variables are global to the entire block and can be used anywhere a PL/SQL variable is allowed. Like host variables in a SQL statement, host variables in a PL/SQL block must be prefixed with a colon. The colon sets host variables apart from PL/SQL variables and database objects.
VARCHAR Variables
When entering a PL/SQL block, Oracle automatically checks the length fields of VARCHAR host variables. Therefore, you must set the length fields before the block is entered. For input variables, set the length field to the length of the value stored in the string field. For output variables, set the length field to the maximum length allowed by the string field.
Indicator Variables
In a PL/SQL block, you cannot refer to an indicator variable by itself; it must be appended to its associated host variable. Further, if you refer to a host variable with its indicator variable, you must always refer to it that way in the same block.
SQLCHECK
You must specify SQLCHECK=SEMANTICS when precompiling a program with an embedded PL/SQL block. You must also use the USERID option. For more information, see Chapter 14, "Precompiler Options".
Advantages of PL/SQL
This section looks at some of the features and benefits offered by PL/SQL, such as:
-
Better performance
-
Integration with Oracle
-
Cursor FOR loops
-
Procedures and functions
-
Packages
-
PL/SQL tables
-
User-defined records
For more information about PL/SQL, see Oracle Database PL/SQL Language Reference.
Better Performance
PL/SQL can help you reduce overhead, improve performance, and increase productivity. For example, without PL/SQL, Oracle must process SQL statements one at a time. Each SQL statement results in another call to the Server and higher overhead. However, with PL/SQL, you can send an entire block of SQL statements to the server. This minimizes communication between your application and the server.
Integration with Oracle
PL/SQL is tightly integrated with the server. For example, most PL/SQL datatypes are native to the data dictionary. Furthermore, you can use the %TYPE attribute to base variable declarations on column definitions stored in the data dictionary, as the following example shows:
job_title emp.job%TYPE;
That way, you need not know the exact datatype of the column. Furthermore, if a column definition changes, the variable declaration changes accordingly and automatically. This provides data independence, reduces maintenance costs, and allows programs to adapt as the database changes.
Cursor FOR Loops
With PL/SQL, you need not use the DECLARE, OPEN, FETCH, and CLOSE statements to define and manipulate a cursor. Instead, you can use a cursor FOR loop, which implicitly declares its loop index as a record, opens the cursor associated with a given query, repeatedly fetches data from the cursor into the record and then closes the cursor. An example follows:
DECLARE
...
BEGIN
FOR emprec IN (SELECT empno, sal, comm FROM emp) LOOP
IF emprec.comm / emprec.sal > 0.25 THEN ...
...
END LOOP;
END;
Notice that you use dot notation to reference fields in the record.
Subprograms
PL/SQL has two types of subprograms called procedures and functions, which aid application development by letting you isolate operations. Generally, you use a procedure to perform an action and a function to compute a value.
Procedures and functions provide extensibility. That is, they let you tailor the PL/SQL language to suit your needs. For example, if you need a procedure that creates a new department, you can write your own, such as follows:
PROCEDURE create_dept
(new_dname IN CHAR(14),
new_loc IN CHAR(13),
new_deptno OUT NUMBER(2)) IS
BEGIN
SELECT deptno_seq.NEXTVAL INTO new_deptno FROM dual;
INSERT INTO dept VALUES (new_deptno, new_dname, new_loc);
END create_dept;
When called, this procedure accepts a new department name and location, selects the next value in a department-number database sequence, inserts the new number, name, and location into the dept table and then returns the new number to the caller.
You can store subprograms in the database (using CREATE FUNCTION and CREATE PROCEDURE) that can be called from multiple applications without needing to be re-compiled each time.
Parameter Modes
You use parameter modes to define the behavior of formal parameters. There are three parameter modes: IN (the default), OUT, and IN OUT. An IN parameter lets you pass values to the subprogram being called. An OUT parameter lets you return values to the caller of a subprogram. An IN OUT parameter lets you pass initial values to the subprogram being called and return updated values to the caller.
The datatype of each actual parameter must be convertible to the datatype of its corresponding formal parameter. Table 6-1 shows the legal conversions between datatypes.
Packages
PL/SQL lets you bundle logically related types, program objects, and subprograms into a package. Packages can be compiled and stored in a database, where their contents can be shared by multiple applications.
Packages usually have two parts: a specification and a body. The specification is the interface to your applications; it declares the types, constants, variables, exceptions, cursors, and subprograms available for use. The body defines cursors and subprograms and so implements the specification. The following example "packages" two employment procedures:
PACKAGE emp_actions IS -- package specification
PROCEDURE hire_employee (empno NUMBER, ename CHAR, ...);
PROCEDURE fire_employee (emp_id NUMBER);
END emp_actions;
PACKAGE BODY emp_actions IS -- package body
PROCEDURE hire_employee (empno NUMBER, ename CHAR, ...) IS
BEGIN
INSERT INTO emp VALUES (empno, ename, ...);
END hire_employee;
PROCEDURE fire_employee (emp_id NUMBER) IS
BEGIN
DELETE FROM emp WHERE empno = emp_id;
END fire_employee;
END emp_actions;
Only the declarations in the package specification are visible and accessible to applications. Implementation details in the package body are hidden and inaccessible.
PL/SQL Tables
PL/SQL provides a composite datatype named TABLE. Objects of type TABLE are called PL/SQL tables, which are modeled as (but not the same as) database tables. PL/SQL tables have only one column and use a primary key to give you array-like access to rows. The column can belong to any scalar type (such as CHAR, DATE, or NUMBER), but the primary key must belong to type BINARY_INTEGER, PLS_INTEGER or VARCHAR2.
You can declare PL/SQL table types in the declarative part of any block, procedure, function, or package. The following example declares a TABLE type called NumTabTyp:
DECLARE
TYPE NumTabTyp IS TABLE OF NUMBER
INDEX BY BINARY_INTEGER;
...
BEGIN
...
END;
Once you define type NumTabTyp, you can declare PL/SQL tables of that type, as the next example shows:
num_tab NumTabTyp;
The identifier num_tab represents an entire PL/SQL table.
You reference rows in a PL/SQL table using array-like syntax to specify the primary key value. For example, you reference the ninth row in the PL/SQL table named num_tab as follows:
num_tab(9) ...
User-Defined Records
You can use the %ROWTYPE attribute to declare a record that represents a row in a database table or a row fetched by a cursor. However, you cannot specify the datatypes of fields in the record or define fields of your own. The composite datatype RECORD lifts those restrictions.
Objects of type RECORD are called records. Unlike PL/SQL tables, records have uniquely named fields, which can belong to different datatypes. For example, suppose you have different kinds of data about an employee such as name, salary, hire date, and so on. This data is dissimilar in type but logically related. A record that contains such fields as the name, salary, and hire date of an employee would let you treat the data as a logical unit.
You can declare record types and objects in the declarative part of any block, procedure, function, or package. The following example declares a RECORD type called DeptRecTyp:
DECLARE
TYPE DeptRecTyp IS RECORD
(deptno NUMBER(4) NOT NULL := 10, -- must initialize
dname CHAR(9),
loc CHAR(14));
Notice that the field declarations are like variable declarations. Each field has a unique name and specific datatype. You can add the NOT NULL option to any field declaration and so prevent the assigning of NULLs to that field. However, you must initialize NOT NULL fields.
Once you define type DeptRecTyp, you can declare records of that type, as the next example shows:
dept_rec DeptRecTyp;
The identifier dept_rec represents an entire record.
You use dot notation to reference individual fields in a record. For example, you reference the dname field in the dept_rec record as follows:
dept_rec.dname ...
Embedding PL/SQL Blocks
Pro*COBOL treats a PL/SQL block like a single embedded SQL statement. Thus, you can place a PL/SQL block anywhere in a host program that you can place a SQL statement.
To embed a PL/SQL block in your host program, simply bracket the PL/SQL block with the keywords EXEC SQL EXECUTE and END-EXEC as follows:
EXEC SQL EXECUTE
DECLARE
...
BEGIN
...
END;
END-EXEC.
When your program embeds PL/SQL blocks, you must specify the precompiler option SQLCHECK=SEMANTICS because PL/SQL must be parsed by Pro*COBOL. To connect to the server, you must also specify the option USERID. For more information, see "Using Pro*COBOL Precompiler Options".
Host Variables and PL/SQL
Host variables are the key to communication between a host language and a PL/SQL block. Host variables can be shared with PL/SQL, meaning that PL/SQL can set and reference host variables.
For example, you can prompt a user for information and use host variables to pass that information to a PL/SQL block. Then, PL/SQL can access the database and use host variables to pass the results back to your host program.
Inside a PL/SQL block, host variables are treated as global to the entire block and can be used anywhere a PL/SQL variable is allowed. Like host variables in a SQL statement, host variables in a PL/SQL block must be prefixed with a colon. The colon sets host variables apart from PL/SQL variables and database objects.
PL/SQL Examples
The following example illustrates the use of host variables with PL/SQL. The program prompts the user for an employee number and then displays the job title, hire date, and salary of that employee.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 USERNAME PIC X(20) VARYING.
01 PASSWORD PIC X(20) VARYING.
01 EMP-NUMBER PIC S9(4) COMP.
01 JOB-TITLE PIC X(20) VARYING.
01 HIRE-DATE PIC X(9) VARYING.
01 SALARY PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
EXEC SQL END DECLARE SECTION END-EXEC.
EXEC SQL INCLUDE SQLCA END-EXEC.
...
DISPLAY 'Connected to Oracle'.
PERFORM
DISPLAY 'Employee Number (0 to end)? 'WITH NO ADVANCING
ACCEPT EMP-NUMBER
IF EMP-NUMBER = 0
EXEC SQL COMMIT WORK RELEASE END-EXEC
DISPLAY 'Exiting program'
STOP RUN
END-IF.
* ---------------- begin PL/SQL block -----------------
EXEC SQL EXECUTE
BEGIN
SELECT job, hiredate, sal
INTO :JOB-TITLE, :HIRE-DATE, :SALARY
FROM EMP
WHERE EMPNO = :EMP-NUMBER;
END;
END-EXEC.
* ---------------- end PL/SQL block -----------------
DISPLAY 'Number Job Title Hire Date Salary'.
DISPLAY '------------------------------------'.
DISPLAY EMP-NUMBER, JOB-TITLE, HIRE-DATE, SALARY.
END-PERFORM.
...
SQL-ERROR.
EXEC SQL WHENEVER SQLERROR CONTINUE END-EXEC.
EXEC SQL ROLLBACK WORK RELEASE END-EXEC.
DISPLAY 'Processing error'.
STOP RUN.
Notice that the host variable EMP-NUMBER is set before the PL/SQL block is entered, and the host variables JOB-TITLE, HIRE-DATE, and SALARY are set inside the block.
A More Complex PL/SQL Example
In the following example the user is prompted for a bank account number, transaction type, and transaction amount. The account is then debited or credited. If the account does not exist, an exception is raised. When the transaction is complete its status is displayed.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 USERNAME PIC X(20) VARYING.
01 ACCT-NUM PIC S9(4) COMP.
01 TRANS-TYPE PIC X(1).
01 TRANS-AMT PIC PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
01 STATUS PIC X(80) VARYING.
EXEC SQL END DECLARE SECTION END-EXEC.
EXEC SQL INCLUDE SQLCA END-EXEC.
DISPLAY 'Username? 'WITH NO ADVANCING.
ACCEPT USERNAME.
DISPLAY 'Password? '.
ACCEPT PASSWORD.
EXEC SQL WHENEVER SQLERROR DO PERFORM SQL-ERROR.
EXEC SQL CONNECT :USERNAME IDENTIFIED BY :PASSWORD.
PERFORM
DISPLAY 'Account Number (0 to end)? '
WITH NO ADVANCING
ACCEPT ACCT_NUM
IF ACCT-NUM = 0
EXEC SQL COMMIT WORK RELEASE END-EXEC
DISPLAY 'Exiting program' WITH NO ADVANCING
STOP RUN
END-IF.
DISPLAY 'Transaction Type - D)ebit or C)redit? '
WITH NO ADVANCING
ACCEPT TRANS-TYPE
DISPLAY 'Transaction Amount? '
ACCEPT trans_amt
* --------------------- begin PL/SQL block -------------------
EXEC SQL EXECUTE
DECLARE
old_bal NUMBER(9,2);
err_msg CHAR(70);
nonexistent EXCEPTION;
BEGIN
IF :TRANS-TYP-TYPE = 'C' THEN -- credit the account
UPDATE accts SET bal = bal + :TRANS-AMT
WHERE acctid = :acct-num;
IF SQL%ROWCOUNT = 0 THEN -- no rows affected
RAISE nonexistent;
ELSE
:STATUs := 'Credit applied';
END IF;
ELSIF :TRANS-TYPe = 'D' THEN -- debit the account
SELECT bal INTO old_bal FROM accts
WHERE acctid = :ACCT-NUM;
IF old_bal >= :TRANS-AMT THEN -- enough funds
UPDATE accts SET bal = bal - :TRANS-AMT
WHERE acctid = :ACCT-NUM;
:STATUS := 'Debit applied';
ELSE
:STATUS := 'Insufficient funds';
END IF;
ELSE
:STATUS := 'Invalid type: ' || :TRANS-TYPE;
END IF;
COMMIT;
EXCEPTION
WHEN NO_DATA_FOUND OR nonexistent THEN
:STATUS := 'Nonexistent account';
WHEN OTHERS THEN
err_msg := SUBSTR(SQLERRM, 1, 70);
:STATUS := 'Error: ' || err_msg;
END;
END-EXEC.
* ------------------- end PL/SQL block -----------------------
DISPLAY 'Status: ', STATUS
END-PERFORM.
...
SQL-ERROR.
EXEC SQL WHENEVER SQLERROR CONTINUE END-EXEC.
EXEC SQL ROLLBACK WORK RELEASE END-EXEC.
DISPLAY 'Processing error'.
STOP RUN.
VARCHAR Pseudotype
Recall that you can use the VARCHAR pseudotype to declare variable-length character strings. If the VARCHAR is an input host variable, you must tell Pro*COBOL what length to expect. Therefore, set the length field to the actual length of the value stored in the string field.
If the VARCHAR is an output host variable, Pro*COBOL automatically sets the length field. However, to use a VARCHAR output host variable in your PL/SQL block, you must initialize the length field before entering the block. Therefore, set the length field to the declared (maximum) length of the VARCHAR, as shown in the following example:
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 EMP-NUM PIC S9(4) COMP.
01 EMP-NAME PIC X(10) VARYING.
01 SALARY PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
...
EXEC SQL END DECLARE SECTION END-EXEC.
PROCEDURE DIVISION.
...
* -- initialize length field
MOVE 10 TO EMP-NAME-LEN.
EXEC SQL EXECUTE
BEGIN
SELECT ename, sal INTO :EMP-NAME, :SALARY
FROM emp
WHERE empno = :EMP-NUM;
...
END;
END-EXEC.
Indicator Variables and PL/SQL
PL/SQL does not need indicator variables because it can manipulate NULLs. For example, within PL/SQL, you can use the IS NULL operator to test for NULLs, as follows:
IF variable IS NULL THEN ...
You can use the assignment operator (:=) to assign NULLs, as follows:
variable := NULL;
However, host languages need indicator variables because they cannot manipulate NULLs. Embedded PL/SQL meets this need by letting you use indicator variables to:
-
Accept NULLs input from a host program
-
Output NULLs or truncated values to a host program
When used in a PL/SQL block, indicator variables are subject to the following rule:
-
If you refer to a host variable with an indicator variable, you must always refer to it that way in the same block.
In the following example, the indicator variable IND-COMM appears with its host variable COMMISSION in the SELECT statement, so it must appear that way in the IF statement:
EXEC SQL EXECUTE
BEGIN
SELECT ename, comm
INTO :EMP-NAME, :COMMISSION:IND-COMM FROM emp
WHERE empno = :EMP-NUM;
IF :COMMISSION:IND-COMM IS NULL THEN ...
...
END;
END-EXEC.
Notice that PL/SQL treats :COMMISSION:IND-COMM like any other simple variable. Though you cannot refer directly to an indicator variable inside a PL/SQL block, PL/SQL checks the value of the indicator variable when entering the block and sets the value correctly when exiting the block.
Handling NULLs
When entering a block, if an indicator variable has a value of -1, PL/SQL automatically assigns a NULL to the host variable. When exiting the block, if a host variable is NULL, PL/SQL automatically assigns a value of -1 to the indicator variable. In the next example, if IND-SAL had a value of -1 before the PL/SQL block was entered, the salary_missing exception is raised. An exception is a named error condition.
EXEC SQL EXECUTE
BEGIN
IF :SALARY:IND-SAL IS NULL THEN
RAISE salary_missing;
END IF;
...
END;
END-EXEC.
Handling Truncated Values
PL/SQL does not raise an exception when a truncated string value is assigned to a host variable. However, if you use an indicator variable, PL/SQL sets it to the original length of the string. The following example the host program will be able to tell, by checking the value of IND-NAME, if a truncated value was assigned to EMP-NAME:
EXEC SQL EXECUTE
DECLARE
...
new_name CHAR(10);
BEGIN
...
:EMP_NAME:IND-NAME := new_name;
...
END;
END-EXEC.
Host Tables and PL/SQL
You can pass input host tables and indicator tables to a PL/SQL block. They can be indexed by a PL/SQL variable of type BINARY_INTEGER or PLS_INTEGER; VARCHAR2 key types are not permitted. Normally, the entire host table is passed to PL/SQL, but you can use the ARRAYLEN statement (discussed later) to specify a smaller table dimension.
Furthermore, you can use a subprogram call to assign all the values in a host table to rows in a PL/SQL table. Given that the table subscript range is m .. n, the corresponding PL/SQL table index range is always 1 .. (n - m + 1). For example, if the table subscript range is 5 .. 10, the corresponding PL/SQL table index range is 1 .. (10 - 5 + 1) or 1 .. 6.
Note: Pro*COBOL does not check your usage of host tables. For instance, no index range checking is done.
In the following example, you pass a host table named salary to a PL/SQL block, which uses the host table in a function call. The function is named median because it finds the middle value in a series of numbers. Its formal parameters include a PL/SQL table named num_tab. The function call assigns all the values in the actual parameter salary to rows in the formal parameter num_tab.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
...
01 SALARY OCCURS 100 TIMES PIC S9(6)V99 COMP-3.
01 MEDIAN-SALARY PIC S9(6)V99 COMP-3.
EXEC SQL END DECLARE SECTION END-EXEC.
* -- populate the host table
EXEC SQL EXECUTE
DECLARE
TYPE NumTabTyp IS TABLE OF REAL
INDEX BY BINARY_INTEGER;
n BINARY_INTEGER;
...
FUNCTION median (num_tab NumTabTyp, n INTEGER)
RETURN REAL IS
BEGIN
* -- compute median
END;
BEGIN
n := 100;
:MEDIAN-SALARY := median(:SALARY END;
END-EXEC.
You can also use a subprogram call to assign all row values in a PL/SQL table to corresponding elements in a host table. For an example, see "Stored PL/SQL and Java Subprograms".
The interface between Host Tables and PL/SQL strictly controls datatypes. The default external type for PIC X is CHARF (fixed length character string) and this can only be mapped to PL/SQL tables of type CHAR.
Table 6-1 shows the legal conversions between row values in a PL/SQL table and elements in a host table. The most notable fact is that you cannot pass a PIC X variable to a table of type VARCHAR2 without using datatype equivalencing to equivalence the variable to VARCHAR2, or using PICX=VARCHAR2 on the command line.
Table 6-1 Legal Datatype Conversions
| PL/SQL Table | - | - | - | - | - | - | - | - |
|---|---|---|---|---|---|---|---|---|
|
Host Table |
CHAR |
DATE |
LONG |
LONG RAW |
NUMBER |
RAW |
ROWID |
VARCHAR2 |
|
CHARF |
X |
- |
- |
- |
- |
- |
- |
- |
|
CHARZ |
X |
- |
- |
- |
- |
- |
- |
- |
|
DATE |
- |
X |
- |
- |
- |
- |
- |
- |
|
DECIMAL |
- |
- |
- |
- |
X |
- |
- |
- |
|
DISPLAY |
- |
- |
- |
- |
X |
- |
- |
- |
|
FLOAT |
- |
- |
- |
- |
X |
- |
- |
- |
|
INTEGER |
- |
- |
- |
- |
- |
- |
- |
- |
|
LONG |
X |
- |
X |
- |
- |
- |
- |
- |
|
LONG VARCHAR |
- |
- |
X |
X |
- |
X |
- |
X |
|
LONG VARRAW |
- |
- |
- |
X |
- |
X |
- |
- |
|
NUMBER |
- |
- |
- |
- |
X |
- |
- |
|
|
RAW |
- |
- |
- |
X |
- |
X |
- |
- |
|
ROWID |
- |
- |
- |
- |
- |
- |
X |
- |
|
STRING |
- |
- |
X |
X |
- |
X |
- |
X |
|
UNSIGNED |
- |
- |
- |
- |
X |
- |
- |
- |
|
VARCHAR |
- |
- |
X |
X |
- |
X |
- |
X |
|
VARCHAR2 |
- |
- |
X |
X |
- |
X |
- |
X |
|
VARNUM |
- |
- |
- |
- |
X |
- |
- |
- |
|
VARRAW |
- |
- |
- |
X |
- |
X |
- |
- |
ARRAYLEN Statement
Suppose you must pass an input host table to a PL/SQL block for processing. By default, when binding such a host table, Pro*COBOL use its declared dimension. However, you might not want to process the entire table. In that case, you can use the ARRAYLEN statement to specify a smaller table dimension. ARRAYLEN associates the host table with a host variable, which stores the smaller dimension. The statement syntax is:
EXEC SQL ARRAYLEN host_array (dimension) EXECUTE END-EXEC.
where dimension is a 4-byte, integer host variable, not a literal or an expression.
The ARRAYLEN statement must appear somewhere after the declarations of host_array and dimension. You cannot specify an offset into the host table. However, you might be able to use COBOL features for that purpose.
The following example uses ARRAYLEN to override the default dimension of a host table named BONUS:
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 BONUS OCCURS 100 TIMES PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
01 MY-DIM PIC S9(9) COMP.
...
EXEC SQL ARRAYLEN BONUS (MY-DIM) END-EXEC.
EXEC SQL END DECLARE SECTION END-EXEC.
* -- populate the host table
...
* -- set smaller table dimension
MOVE 25 TO MY-DIM.
EXEC SQL EXECUTE
DECLARE
TYPE NumTabTyp IS TABLE OF REAL
INDEX BY BINARY_INTEGER;
median_bonus REAL;
FUNCTION median (num_tab NumTabTyp, n INTEGER)
RETURN REAL IS
BEGIN
* -- compute median
END;
BEGIN
median_bonus := median(:BONUS, :MY-DIM);
...
END;
END-EXEC.
Only 25 table elements are passed to the PL/SQL block because ARRAYLEN reduces the host table from 100 to 25 elements. As a result, when the PL/SQL block is sent to the server for execution, a much smaller host table is sent along. This saves time and, in a networked environment, reduces network traffic.
Optional Keyword EXECUTE to ARRAYLEN Statement
The use of host tables used in a dynamic SQL Method 2 statement (see "Using Method 2") may have two different interpretations based on the presence or absence of the keyword to EXECUTE the ARRAYLEN statement. .
If the EXECUTE keyword is absent:
-
The PL/SQL block will be executed multiple times, with the actual number determined by the minimum dimension of ARRAYLEN used.
-
The host array cannot be bound to a PL/SQL table.
If EXECUTE is present:
-
The host table must be bound to an index table.
-
The PL/SQL block will be executed once.
-
All host variables specified in the EXEC SQL EXECUTE statement must:
-
Be specified in an ARRAYLEN ... EXECUTE statement, or
-
Be a scalar.
-
The following Pro*COBOL example demonstrates how host tables can be used to determine how many times a given PL/SQL block is executed. In this case, the PL/SQL block will be execute 3 times resulting in 3 new rows in the emp table.
...
01 DYNSTMT PIC X(80) VARYING.
01 EMPNOTAB PIC S9(4) COMPUTATIONAL OCCURS 5 TIMES.
01 ENAMETAB PIC X(10) OCCURS 3 TIMES.
...
MOVE 1111 TO EMPNOTAB(1).
MOVE 2222 TO EMPNOTAB(2).
MOVE 3333 TO EMPNOTAB(3).
MOVE 4444 TO EMPNOTAB(4).
MOVE 5555 TO EMPNOTAB(5).
MOVE "MICKEY" TO ENAMETAB(1).
MOVE "MINNIE" TO ENAMETAB(2).
MOVE "GOOFY" TO ENAMETAB(3).
MOVE "BEGIN INSERT INTO emp(empno, ename) VALUES :b1, :b2; END;"
TO DYNSTMT-ARR.
MOVE 57 TO DYNSTMT-LEN.
EXEC SQL PREPARE s1 FROM :DYNSTMT END-EXEC.
EXEC SQL EXECUTE s1 USING :EMPNOTAB, :ENAMETAB END-EXEC.
...
Given the following PL/SQL procedure:
CREATE OR REPLACE PACKAGE pkg AS
TYPE tab IS TABLE OF NUMBER(5) INDEX BY BINARY_INTEGER;
PROCEDURE proc1 (parm1 tab, parm2 NUMBER, parm3 tab);
END;
The following Pro*COBOL example demonstrates how to bind a host table to a PL/SQL index table through dynamic method 2. Note the presence of the ARRAYLEN...EXECUTE statement for all host arrays specified in the EXEC SQL EXECUTE statement.
...
01 DYNSTMT PIC X(80) VARYING.
01 II PIC S9(4) COMP VALUE 2.
01 INTTAB PIC S9(9) COMP OCCURS 3 TIMES.
01 DIM PIC S9(9) COMP VALUE 3.
EXEC SQL ARRAYLEN INTTAB (DIM) EXECUTE END-EXEC.
...
MOVE 1 TO INTTAB(1).
MOVE 2 TO INTTAB(2).
MOVE 3 TO INTTAB(3).
MOVE "BEGIN pkg.proc1 (:v1, :v2, :v3); end;";
TO DYNSTMT-ARR.
MOVE 37 TO DYNSTMT-LEN.
EXEC SQL PREPARE s1 FROM :DYNSTMT END-EXEC.
EXEC SQL EXECUTE s1 USING :INTTAB, :II, :INTTAB END-EXEC.
...
However, the following Pro*COBOL example will result in a precompile-time error because there is no ARRAYLEN...EXECUTE statement for INTTAB2.
...
01 DYNSTMT PIC X(80) VARYING.
01 INTTAB PIC S9(9) COMP OCCURS 3 TIMES.
01 INTTAB2 PIC S9(9) COMP OCCURS 3 TIMES.
01 DIM PIC S9(9) COMP VALUE 3.
EXEC SQL ARRAYLEN INTTAB (DIM) EXECUTE END-EXEC.
...
MOVE 1 TO INTTAB(1).
MOVE 2 TO INTTAB(2).
MOVE 3 TO INTTAB(3).
MOVE "BEGIN pkg.proc1 (:v1, :v2, :v3); end;";
TO DYNSTMT-ARR.
MOVE 37 TO DYNSTMT-LEN.
EXEC SQL PREPARE s1 FROM :DYNSTMT END-EXEC.
EXEC SQL EXECUTE s1 USING :INTTAB, :INTTAB2, :INTTAB END-EXEC.
...
Cursor Usage in Embedded PL/SQL
The maximum number of cursors your program can simultaneously use is determined by the database initialization parameter OPEN_CURSORS. Normally, to prevent OPEN_CURSORS being exceeded, the precompiler allows management of statement cursors. The precompiler options HOLD_CURSOR, RELEASE_CURSOR and MAXOPENCURSORS are used. (For more details on this subject, see "Embedded PL/SQL Considerations".) While executing an embedded PL/SQL block there will be one cursor, the parent cursor, associated with the entire PL/SQL block and a separate child cursor for each statement executed during the execution of the PL/SQL block. Because the PL/SQL block is passed to the server for execution, only the parent cursor can be tracked by the precompiler runtime library. Thus, it is possible for applications that use a lot of cursors in this way to exceed OPEN_CURSORS. Figure 6-1 shows how to calculate the maximum number of cursors used.
Developers should be aware of this situation and plan for this in the setting of OPEN_CURSORS and MAXOPENCURSORS.
If there are problems with this, you may wish to free all child cursors after a SQL statement is executed.
This can be achieved by setting RELEASE_CURSOR=YES and HOLD_CURSOR=NO. Because the use of the first setting for the entire program is likely to have an impact on performance, you can set these options in line as follows:
EXEC ORACLE OPTION (RELEASE_CURSOR=YES) END-EXEC.
* -- first embedded PL/SQL block
EXEC ORACLE OPTION (RELEASE_CURSOR=NO)END-EXEC.
* -- embedded SQL statements
EXEC ORACLE OPTION (RELEASE_CURSOR=YES)END-EXEC.
* -- second embedded PL/SQL block
EXEC ORACLE OPTION (RELEASE_CURSOR=NO)END-EXEC.
* -- embedded SQL statements
Stored PL/SQL and Java Subprograms
Unlike anonymous blocks, PL/SQL subprograms (procedures and functions) and Java methods can be compiled separately, stored in the database, and invoked.
A subprogram explicitly created using an Oracle tool such as SQL*Plus is called a stored subprogram. Once compiled and stored in the data dictionary, it is a database object can be re-executed without being re-compiled.
When a subprogram within a PL/SQL block or stored subprogram is sent to the database by your application, it is called an inline subprogram and is compiled by the database. Pro*COBOL sends the statement to the server for execution.
Subprograms defined within a package are considered part of the package, and so are called packaged subprograms. Stored subprograms not defined within a package are called standalone subprograms.
Creating Stored Subprograms
You can embed the SQL statements CREATE FUNCTION, CREATE PROCEDURE, and CREATE PACKAGE in a COBOL program, as the following example shows:
EXEC SQL CREATE
FUNCTION sal_ok (salary REAL, title CHAR)
RETURN BOOLEAN AS
min_sal REAL;
max_sal REAL;
BEGIN
SELECT losal, hisal INTO min_sal, max_sal
FROM sals
WHERE job = title;
RETURN (salary >= min_sal) AND
(salary <= max_sal);
END sal_ok;
END-EXEC.
Notice that the embedded CREATE {FUNCTION | PROCEDURE | PACKAGE} statement is a hybrid. Like all other embedded CREATE statements, it begins with the keywords EXEC SQL (not EXEC SQL EXECUTE).
If an embedded CREATE {FUNCTION | PROCEDURE | PACKAGE} statement fails, Oracle generates a warning, not an error. For the full syntax of the CREATE statement see the Oracle Database SQL Language Reference.
Calling a Stored PL/SQL or Java Subprogram
To call a stored subprogram from your host program, you can use either an anonymous PL/SQL block or the CALL embedded SQL statement.
Anonymous PL/SQL Block
The following example calls a standalone procedure named raise_salary:
EXEC SQL EXECUTE
BEGIN
raise_salary(:emp_id, :increase);
END;
END-EXEC.
Notice that stored subprograms can take parameters. In this example, the actual parameters emp_id and increase are host variables.
In the next example, the procedure raise_salary is stored in a package named emp_actions, so you must use dot notation to fully qualify the procedure call:
EXEC SQL EXECUTE
BEGIN
emp_actions.raise_salary(:emp_id, :increase);
END;
END-EXEC.
An actual IN parameter can be a literal, host variable, host table, PL/SQL constant or variable, PL/SQL table, PL/SQL user-defined record, subprogram call, or expression. However, an actual OUT parameter cannot be a literal, subprogram call, or expression.
You must use precompiler option SQLCHECK=SEMANTICS with an embedded PL/SQL block.
CALL Statement
The concepts presented earlier for the embedded PL/SQL block holds true for the CALL statement. The CALL embedded SQL statement has the form:
EXEC SQL
CALL [schema.][package.]stored_proc[@db_link](arg1, ...)
[INTO :ret_var[[INDICATOR]:ret_ind]]
END-EXEC.
where:
schema
the schema containing the procedure
package
the package containing the procedure
stored_proc
is the Java or PL/SQL stored procedure to be called
db_link
is the optional remote database link
arg1...
is the list of arguments (variables, literals, or expressions) passed,
ret_var
is the optional host variable which receives the result
ind_var
the optional indicator variable for ret_var.
You can use either SQLCHECK=SYNTAX, or SQLCHECK=SEMANTICS with the CALL statement.
CALL Example
If you have created a PL/SQL function fact (stored in the package mathpkg) that takes an integer as input and returns its factorial in an integer:
EXEC SQL CREATE OR REPLACE PACKAGE BODY mathpkg as
function fact(n IN INTEGER) RETURN INTEGER AS
BEGIN
IF (n <= 0) then return 1;
ELSE return n * fact(n - 1);
END IF;
END fact;
END mathpkge;
END-EXEC.
then to use fact in a Pro*COBOL application:
...
01 N PIC S9(4) COMP.
01 FACT PIC S9(9) COMP.
...
EXEC SQL CALL mathpkge.fact(:N) INTO :FACT END-EXEC.
...
For more information about this statement, see "CALL (Executable Embedded SQL)". For a complete explanation of passing arguments and other issues, see Oracle Database Advanced Application Developer's Guide, "External Routines" chapter.
Using Dynamic PL/SQL
Recall that Pro*COBOL treats an entire PL/SQL block like a single SQL statement. Therefore, you can store a PL/SQL block in a string host variable. Then, if the block contains no host variables, you can use dynamic SQL Method 1 to execute the PL/SQL string. Or, if the block contains a known number of host variables, you can use dynamic SQL Method 2 to prepare and execute the PL/SQL string. If the block contains an unknown number of host variables, you must use dynamic SQL Method 4. For more information, refer to Chapter 9, "Oracle Dynamic SQL", Chapter 10, "ANSI Dynamic SQL"and Chapter 11, "Oracle Dynamic SQL: Method 4".
Sample Program 9: Calling a Stored Procedure
Before trying the sample program, you must create a PL/SQL package named calldemo, by running the following script, titled CALLDEMO.SQL, which is supplied with Pro*COBOL. The script can be found in the Pro*COBOL demo library. Check your system-specific Oracle documentation for exact spelling of the the name of the script.
CREATE OR REPLACE PACKAGE calldemo AS
TYPE name_array IS TABLE OF emp.ename%type
INDEX BY BINARY_INTEGER;
TYPE job_array IS TABLE OF emp.job%type
INDEX BY BINARY_INTEGER;
TYPE sal_array IS TABLE OF emp.sal%type
INDEX BY BINARY_INTEGER;
PROCEDURE get_employees(
dept_number IN number, -- department to query
batch_size IN INTEGER, -- rows at a time
found IN OUT INTEGER, -- rows actually returned
done_fetch OUT INTEGER, -- all done flag
emp_name OUT name_array,
job OUT job_array,
sal OUT sal_array);
END calldemo;
/
CREATE OR REPLACE PACKAGE BODY calldemo AS
CURSOR get_emp (dept_number IN number) IS
SELECT ename, job, sal FROM emp
WHERE deptno = dept_number;
-- Procedure "get_employees" fetches a batch of employee
-- rows (batch size is determined by the client/caller
-- of the procedure). It can be called from other
-- stored procedures or client application programs.
-- The procedure opens the cursor if it is not
-- already open, fetches a batch of rows, and
-- returns the number of rows actually retrieved. At
-- end of fetch, the procedure closes the cursor.
PROCEDURE get_employees(
dept_number IN number,
batch_size IN INTEGER,
found IN OUT INTEGER,
done_fetch OUT INTEGER,
emp_name OUT name_array,
job OUT job_array,
sal OUT sal_array) IS
BEGIN
IF NOT get_emp%ISOPEN THEN -- open the cursor if
OPEN get_emp(dept_number); -- not already open
END IF;
-- Fetch up to "batch_size" rows into PL/SQL table,
-- tallying rows found as they are retrieved. When all
-- rows have been fetched, close the cursor and exit
-- the loop, returning only the last set of rows found.
done_fetch := 0; -- set the done flag FALSE
found := 0;
FOR i IN 1..batch_size LOOP
FETCH get_emp INTO emp_name(i), job(i), sal(i);
IF get_emp%NOTFOUND THEN -- if no row was found
CLOSE get_emp;
done_fetch := 1; -- indicate all done
EXIT;
ELSE
found := found + 1; -- count row
END IF;
END LOOP;
END;
END;
/
The following sample program connects to the database, prompts the user for a department number and then calls a PL/SQL procedure named get_employees, which is stored in package calldemo. The procedure declares three PL/SQL tables as OUT formal parameters and then fetches a batch of employee data into the PL/SQL tables. The matching actual parameters are host tables. When the procedure finishes, row values in the PL/SQL tables are automatically assigned to the corresponding elements in the host tables. The program calls the procedure repeatedly, displaying each batch of employee data, until no more data is found.
*****************************************************************
* Sample Program 9: Calling a Stored Procedure
*
* This program connects to ORACLE, prompts the user for a
* department number, then calls a PL/SQL stored procedure named
* GET_EMPLOYEES, which is stored in package CALLDEMO. The
* procedure declares three PL/SQL tables ast OUT formal
* parameters, then fetches a batch of employee data into the
* PL/SQL tables. The matching actual parameters are host tables.
* When the procedure finishes, it automatically assigns all row
* values in the PL/SQL tables to corresponding elements in the
* host tables. The program calls the procedure repeatedly,
* displaying each batch of employee data, until no more data
* is found.
* Use option picx=varchar2 when precompiling this sample program.
*****************************************************************
IDENTIFICATION DIVISION.
PROGRAM-ID. CALL-STORED-PROC.
ENVIRONMENT DIVISION.
DATA DIVISION.
WORKING-STORAGE SECTION.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 USERNAME PIC X(15) VARYING.
01 PASSWD PIC X(15) VARYING.
01 DEPT-NUM PIC S9(9) COMP.
01 EMP-TABLES.
05 EMP-NAME OCCURS 10 TIMES PIC X(10).
05 JOB-TITLE OCCURS 10 TIMES PIC X(10).
05 SALARY OCCURS 10 TIMES COMP-2.
01 DONE-FLAG PIC S9(9) COMP.
01 TABLE-SIZE PIC S9(9) COMP VALUE 10.
01 NUM-RET PIC S9(9) COMP.
01 SQLCODE PIC S9(9) COMP.
EXEC SQL END DECLARE SECTION END-EXEC.
01 COUNTER PIC S9(9) COMP.
01 DISPLAY-VARIABLES.
05 D-EMP-NAME PIC X(10).
05 D-JOB-TITLE PIC X(10).
05 D-SALARY PIC Z(5)9.
05 D-DEPT-NUM PIC 9(2).
EXEC SQL INCLUDE SQLCA END-EXEC.
PROCEDURE DIVISION.
BEGIN-PGM.
EXEC SQL WHENEVER SQLERROR DO
PERFORM SQL-ERROR END-EXEC.
PERFORM LOGON.
PERFORM INIT-TABLES VARYING COUNTER FROM 1 BY 1
UNTIL COUNTER > 10.
PERFORM GET-DEPT-NUM.
PERFORM DISPLAY-HEADER.
MOVE ZERO TO DONE-FLAG.
MOVE ZERO TO NUM-RET.
PERFORM FETCH-BATCH UNTIL DONE-FLAG = 1.
PERFORM LOGOFF.
INIT-TABLES.
MOVE SPACE TO EMP-NAME(COUNTER).
MOVE SPACE TO JOB-TITLE(COUNTER).
MOVE ZERO TO SALARY(COUNTER).
GET-DEPT-NUM.
MOVE ZERO TO DEPT-NUM.
DISPLAY " ".
DISPLAY "ENTER DEPARTMENT NUMBER: "
WITH NO ADVANCING.
ACCEPT D-DEPT-NUM.
MOVE D-DEPT-NUM TO DEPT-NUM.
DISPLAY-HEADER.
DISPLAY " ".
DISPLAY "EMPLOYEE JOB TITLE SALARY".
DISPLAY "-------- --------- ------".
FETCH-BATCH.
EXEC SQL EXECUTE
BEGIN
CALLDEMO.GET_EMPLOYEES
(:DEPT-NUM, :TABLE-SIZE,
:NUM-RET, :DONE-FLAG,
:EMP-NAME, :JOB-TITLE, :SALARY);
END;
END-EXEC.
PERFORM PRINT-ROWS VARYING COUNTER FROM 1 BY 1
UNTIL COUNTER > NUM-RET.
PRINT-ROWS.
MOVE EMP-NAME(COUNTER) TO D-EMP-NAME.
MOVE JOB-TITLE(COUNTER) TO D-JOB-TITLE.
MOVE SALARY(COUNTER) TO D-SALARY.
DISPLAY D-EMP-NAME, " ",
D-JOB-TITLE, " ",
D-SALARY.
LOGON.
MOVE "SCOTT" TO USERNAME-ARR.
MOVE 5 TO USERNAME-LEN.
MOVE "TIGER" TO PASSWD-ARR.
MOVE 5 TO PASSWD-LEN.
EXEC SQL
CONNECT :USERNAME IDENTIFIED BY :PASSWD
END-EXEC.
DISPLAY " ".
DISPLAY "CONNECTED TO ORACLE AS USER: ", USERNAME-ARR.
LOGOFF.
DISPLAY " ".
DISPLAY "HAVE A GOOD DAY.".
DISPLAY " ".
EXEC SQL COMMIT WORK RELEASE END-EXEC.
STOP RUN.
SQL-ERROR.
EXEC SQL WHENEVER SQLERROR CONTINUE END-EXEC.
DISPLAY " ".
DISPLAY "ORACLE ERROR DETECTED:".
DISPLAY " ".
DISPLAY SQLERRMC.
EXEC SQL ROLLBACK WORK RELEASE END-EXEC.
STOP RUN.
Remember that the datatype of each actual parameter must be convertible to the datatype of its corresponding formal parameter. Further, before a stored subprogram exits, all OUT formal parameters must be assigned values. Otherwise, the values of corresponding actual parameters are indeterminate.
Remote Access
PL/SQL lets you access remote databases through database links. Typically, database links are established by your DBA and stored in the data dictionary. A database link tells your program where the remote database is located, the path to it, and what username and password to use. The following example uses the database link dallas to call the raise_salary procedure:
EXEC SQL EXECUTE
BEGIN
raise_salary@dallas(:emp_id, :increase);
END;
END-EXEC.
You can create synonyms to provide location transparency for remote subprograms, as the following example shows:
CREATE PUBLIC SYNONYM raise_salary FOR raise_salary@dallas;
Cursor Variables
You can use cursor variables in your Pro*COBOL programs to process multi-row queries using static embedded SQL. A cursor variable identifies a cursor reference that is defined and opened on the database server, using PL/SQL. See Oracle Database PL/SQL Language Reference for complete information about cursor variables.
Like a cursor, a cursor variable points to the current row in the active set of a multi-row query. Cursors differ from cursor variables the way constants differ from variables. While a cursor is static, a cursor variable is dynamic, because it is not tied to a specific query. You can open a cursor variable for any type-compatible query.
You can assign new values to a cursor variable and pass it as a parameter to subprograms, including subprograms stored in a database. This gives you a convenient way to centralize data retrieval.
First, you declare the cursor variable. After declaring the variable, you use these statements to control a cursor variable:
-
ALLOCATE
-
OPEN ... FOR
-
FETCH
-
CLOSE
-
FREE
After you declare the cursor variable and allocate memory for it, you must pass it as an input host variable (bind variable) to PL/SQL, OPEN it FOR a multi-row query on the server side, FETCH from it on the client side and then CLOSE it on either side.
The advantages of cursor variables are
-
Ease of maintenance. Queries are centralized, in the stored procedure that opens the cursor variable. If you need to change the cursor, you only need to make the change in one place: the stored procedure. There is no need to change each application.
-
Increased Security. The user of the application (the username when the Pro*COBOL application connected to the database) must have execute permission on the stored procedure that opens the cursor. This user, however, does not need to have read permission on the tables used in the query. This capability can be used to limit access to the columns in the table.
Declaring a Cursor Variable
You declare a Pro*COBOL cursor variable using the SQL-CURSOR pseudotype. For example:
WORKING-STORAGE SECTION.
...
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
...
01 CUR-VAR SQL-CURSOR.
...
EXEC SQL END DECLARE SECTION END-EXEC.
A SQL-CURSOR variable is implemented as a COBOL group item in the code that Pro*COBOL generates. A cursor variable is just like any other Pro*COBOL host variable.
Allocating a Cursor Variable
Before you can OPEN or FETCH from a cursor variable, you must initialize it using the Pro*COBOL ALLOCATE command. For example, to initialize the cursor variable CUR-VAR that was declared in the previous section, write the following statement:
EXEC SQL ALLOCATE :CUR-VAR END-EXEC.
Allocating a cursor variable does not require a call to the server, either at precompile time or at runtime.
The AT clause cannot be used in an ALLOCATE statement.
Caution: Allocating a cursor variable does cause heap memory to be used. For this reason, avoid allocating a cursor variable in a program loop.
Opening a Cursor Variable
You must use an embedded anonymous PL/SQL block to open a cursor variable on the database server. The anonymous PL/SQL block may open the cursor either indirectly by calling a PL/SQL stored procedure that opens the cursor (and defines it in the same statement) or directly from the Pro*COBOL program.
Opening Indirectly through a Stored PL/SQL Procedure
Consider the following PL/SQL package stored in the database:
CREATE PACKAGE demo_cur_pkg AS
TYPE EmpName IS RECORD (name VARCHAR2(10));
TYPE cur_type IS REF CURSOR RETURN EmpName;
PROCEDURE open_emp_cur (
curs IN OUT curtype,
dept_num IN number);
END;
CREATE PACKAGE BODY demo_cur_pkg AS
CREATE PROCEDURE open_emp_cur (
curs IN OUT curtype,
dept_num IN number) IS
BEGIN
OPEN curs FOR
SELECT ename FROM emp
WHERE deptno = dept_num
ORDER BY ename ASC;
END;
END;
After this package has been stored, you can open the cursor curs by first calling the open_emp_cur stored procedure from your Pro*COBOL program and then issuing a FETCH from the cursor variable emp_cursor in the program. For example:
WORKING-STORAGE SECTION.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 emp_cursor sql-cursor.
01 DEPT-NUM PIC S9(4).
01 EMP-NAME PIC X(10) VARYING.
EXEC SQL END DECLARE SECTION END-EXEC.
...
PROCEDURE DIVISION.
...
* Allocate the cursor variable.
EXEC SQL
ALLOCATE :emp-cursor
END-EXEC.
...
MOVE 30 TO dept_num.
* Open the cursor on the Oracle Server.
EXEC SQL EXECUTE
begin
demo_cur_pkg.open_emp_cur(:emp-cursor, :dept-num);
END;
END-EXEC.
EXEC SQL
WHENEVER NOT FOUND DO PERFORM SIGN-OFF
END-EXEC.
FETCH-LOOP.
EXEC SQL
FETCH :emp_cursor INTO :EMP-NAME
END-EXEC.
DISPLAY "Employee Name: ",:EMP-NAME.
GO TO FETCH-LOOP.
...
SIGN-OFF.
...
Opening Directly from Your Pro*COBOL Application
To open a cursor using a PL/SQL anonymous block in a Pro*COBOL program, define the cursor in the anonymous block. Consider the following example:
PROCEDURE DIVISION.
...
EXEC SQL EXECUTE
begin
OPEN :emp_cursor FOR SELECT ename FROM emp
WHERE deptno = :DEPT-NUM;
end;
END-EXEC.
...
Fetching from a Cursor Variable
After opening a cursor variable for a multi-row query, you use the FETCH statement to retrieve rows as you would from a static cursor. The syntax follows:
EXEC SQL FETCH cursor_variable_name
INTO {record_name | variable_name[, variable_name, ...]}
END-EXEC.
Each column value returned by the cursor variable is assigned to a corresponding field or variable in the INTO clause, providing that their datatypes are compatible.
The FETCH statement must be executed on the client side. The following example fetches rows into a host record named EMP-REC:
* -- exit loop when done fetching
EXEC SQL
WHENEVER NOT FOUND DO PERFORM NO-MORE
END-EXEC.
PERFORM
* -- fetch row into record
EXEC SQL FETCH :EMP-CUR INTO :EMP-REC END-EXEC
* -- test for transfer out of loop
...
* -- process the data
...
END-PERFORM.
...
NO-MORE.
...
Use the embedded SQL FETCH .... INTO command to retrieve the rows selected when you opened the cursor variable. For example:
EXEC SQL
FETCH :emp_cursor INTO :EMP-INFO:EMP-INFO-IND
END-EXEC.
Before you can FETCH from a cursor variable, the variable must be initialized and opened. You cannot FETCH from an unopened cursor variable.
Closing a Cursor Variable
Use the embedded SQL CLOSE statement to close a cursor variable. At this point its active set becomes undefined. The syntax follows:
EXEC SQL CLOSE cursor_variable_name END-EXEC.
The CLOSE statement can be executed on the client side or the server side. The following example closes the cursor variable CUR-VAR when the last row is processed:
WORKING-STORAGE SECTION.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
* Declare the cursor variable.
01 CUR-VAR SQL-CURSOR.
...
EXEC SQL END DECLARE SECTION END-EXEC.
PROCEDURE DIVISION.
* Allocate and open the cursor variable, then
* Fetch one or more rows.
...
* Close the cursor variable.
EXEC SQL
CLOSE :CUR-VAR
END-EXEC.
Freeing a Cursor Variable
To free memory allocated for the cursor variable, CUR-VAR, use the FREE statement after the CLOSE:
* Free the cursor variable memory.
EXEC SQL
FREE :CUR-VAR
END-EXEC.
Restrictions on Cursor Variables
The following restrictions apply to the use of cursor variables:
-
Cursor variables are not supported in dynamic SQL.
-
You can only use cursor variables with the ALLOCATE, FETCH, FREE, and CLOSE commands. The DECLARE CURSOR command does not apply to cursor variables.
-
You cannot use the AT clause with the ALLOCATE command.
Sample Program 11: Cursor Variables
The following sample programs—a SQL script (SAMPLE11.sql) and a Pro*COBOL program (SAMPLE11.pco)—demonstrate how you can use cursor variables in Pro*COBOL.
SAMPLE11.SQL
Following is the PL/SQL source code for a creating a package that declares and opens a cursor variable:
CONNECT SCOTT/TIGER
CREATE OR REPLACE PACKAGE emp_demo_pkg AS
TYPE emp_cur_type IS REF CURSOR RETURN emp%ROWTYPE;
PROCEDURE open_cur (
cursor IN OUT emp_cur_type,
dept_num IN number);
END emp_demo_pkg;
/
CREATE OR REPLACE PACKAGE BODY emp_demo_pkg AS
PROCEDURE open_cur (
cursor IN OUT emp_cur_type,
dept_num IN number) IS
BEGIN
OPEN cursor FOR SELECT * FROM emp
WHERE deptno = dept_num
ORDER BY ename ASC;
END;
END emp_demo_pkg;
/
SAMPLE11.PCO
Following is a Pro*COBOL sample program, SAMPLE11.PCO, that uses the cursor variable declared in the SAMPLE11.sql example to fetch employee names, salaries, and commissions from the EMP table:
*****************************************************************
* Sample Program 11: Cursor Variable Operations *
* *
* This program logs on to ORACLE, allocates and opens a cursor *
* variable fetches the names, salaries, and commissions of all *
* salespeople, displays the results, then closes the cursor. *
*****************************************************************
IDENTIFICATION DIVISION.
PROGRAM-ID. CURSOR-VARIABLES.
ENVIRONMENT DIVISION.
DATA DIVISION.
WORKING-STORAGE SECTION.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
01 USERNAME PIC X(15) VARYING.
01 PASSWD PIC X(15) VARYING.
01 HOST PIC X(15) VARYING.
01 EMP-CUR SQL-CURSOR.
01 EMP-INFO.
05 EMP-NUM PIC S9(4) COMP.
05 EMP-NAM PIC X(10) VARYING.
05 EMP-JOB PIC X(10) VARYING.
05 EMP-MGR PIC S9(4) COMP.
05 EMP-DAT PIC X(10) VARYING.
05 EMP-SAL PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
05 EMP-COM PIC S9(6)V99
DISPLAY SIGN LEADING SEPARATE.
05 EMP-DEP PIC S9(4) COMP.
01 EMP-INFO-IND.
05 EMP-NUM-IND PIC S9(4) COMP.
05 EMP-NAM-IND PIC S9(4) COMP.
05 EMP-JOB-IND PIC S9(4) COMP.
05 EMP-MGR-IND PIC S9(4) COMP.
05 EMP-DAT-IND PIC S9(4) COMP.
05 EMP-SAL-IND PIC S9(4) COMP.
05 EMP-COM-IND PIC S9(4) COMP.
05 EMP-DEP-IND PIC S9(4) COMP.
EXEC SQL END DECLARE SECTION END-EXEC.
EXEC SQL INCLUDE SQLCA END-EXEC.
01 DISPLAY-VARIABLES.
05 D-DEP-NUM PIC Z(3)9.
05 D-EMP-NAM PIC X(10).
05 D-EMP-SAL PIC Z(4)9.99.
05 D-EMP-COM PIC Z(4)9.99.
05 D-EMP-DEP PIC 9(2).
PROCEDURE DIVISION.
BEGIN-PGM.
EXEC SQL
WHENEVER SQLERROR DO PERFORM SQL-ERROR
END-EXEC.
PERFORM LOGON.
EXEC SQL
ALLOCATE :EMP-CUR
END-EXEC.
DISPLAY "Enter department number (0 to exit): "
WITH NO ADVANCING.
ACCEPT D-EMP-DEP.
MOVE D-EMP-DEP TO EMP-DEP.
IF EMP-DEP <= 0
GO TO SIGN-OFF
END-IF.
MOVE EMP-DEP TO D-DEP-NUM.
EXEC SQL EXECUTE
BEGIN
emp_demo_pkg.open_cur(:EMP-CUR, :EMP-DEP);
END;
END-EXEC.
DISPLAY " ".
DISPLAY "For department ", D-DEP-NUM, ":".
DISPLAY " ".
DISPLAY "EMPLOYEE SALARY COMMISSION".
DISPLAY "---------- ---------- ----------".
FETCH-LOOP.
EXEC SQL
WHENEVER NOT FOUND GOTO CLOSE-UP
END-EXEC.
MOVE SPACES TO EMP-NAM-ARR.
EXEC SQL FETCH :EMP-CUR
INTO :EMP-NUM:EMP-NUM-IND,
:EMP-NAM:EMP-NAM-IND,
:EMP-JOB:EMP-JOB-IND,
:EMP-MGR:EMP-MGR-IND,
:EMP-DAT:EMP-DAT-IND,
:EMP-SAL:EMP-SAL-IND,
:EMP-COM:EMP-COM-IND,
:EMP-DEP:EMP-DEP-IND
END-EXEC.
MOVE EMP-SAL TO D-EMP-SAL.
IF EMP-COM-IND = 0
MOVE EMP-COM TO D-EMP-COM
DISPLAY EMP-NAM-ARR, " ", D-EMP-SAL,
" ", D-EMP-COM
ELSE
DISPLAY EMP-NAM-ARR, " ", D-EMP-SAL,
" N/A"
END-IF.
GO TO FETCH-LOOP.
LOGON.
MOVE "SCOTT" TO USERNAME-ARR.
MOVE 5 TO USERNAME-LEN.
MOVE "TIGER" TO PASSWD-ARR.
MOVE 5 TO PASSWD-LEN.
MOVE "INST1_ALIAS" TO HOST-ARR.
MOVE 11 TO HOST-LEN.
EXEC SQL
CONNECT :USERNAME IDENTIFIED BY :PASSWD
END-EXEC.
DISPLAY " ".
DISPLAY "CONNECTED TO ORACLE AS USER: ", USERNAME-ARR.
CLOSE-UP.
EXEC SQL
CLOSE :EMP-CUR
END-EXEC.
EXEC SQL
FREE :EMP-CUR
END-EXEC.
SIGN-OFF.
DISPLAY " ".
DISPLAY "HAVE A GOOD DAY.".
DISPLAY " ".
EXEC SQL
COMMIT WORK RELEASE
END-EXEC.
STOP RUN.
SQL-ERROR.
EXEC SQL
WHENEVER SQLERROR CONTINUE
END-EXEC.
DISPLAY " ".
DISPLAY "ORACLE ERROR DETECTED:".
DISPLAY " ".
DISPLAY SQLERRMC.
EXEC SQL
ROLLBACK WORK RELEASE
END-EXEC.
STOP RUN.