Describe Method

Applies To

OraDatabase Object

Description

Describes a schema object. This method returns an instance of the OraMetaData interface.

Usage

OraMetaDataObj = OraDatabase.Describe(SchemaObjectName)

Arguments

The arguments for the method are:

Arguments Description
[in] SchemaObjectName A String representing the name of the schema object to be described.

Remarks

The following schema object types can be described:

  • Tables

  • Views

  • Procedures

  • Functions

  • Packages

  • Sequences

  • Collections (VARRAYs or nested tables)

  • Types

Describing any other schema object (for example, a column) or an invalid schema object name raises an error. You should navigate to schema objects not listed here, rather than describing them directly.

This method takes the name of a schema object, such as emp, and returns a COM Automation object (OraMetaData). The OraMetaData object provides methods for dynamically navigating and accessing all the attributes (OraMDAttribute collection) of a schema object described.

Examples

Simple Describe Example

The following Visual Basic code illustrates a how to use the Describe method to retrieve and display several attributes of the emp table.

Set emp = OraDatabase.Describe("emp") 
 
'Display the name of the Tablespace 
MsgBox emp!tablespace 
'Display name and data type of each column in the emp table. 
Set empColumns = emp!ColumnList 
Set ColumnList = empColumns.Value 
 
for i = 0 to ColumnList.Count - 1 
  Set Column = ColumnList(i).Value 
  MsgBox "Column: " & Column!Name & " Data Type: " & Column!Data Type 
Next i

Describing a Table Example

Before running the following example, make sure that you have the necessary datatypes and tables in the database. See "Schema Objects Used in OraMetaData Examples".

Dim OraSession As OraSession 
Dim OraDatabase As OraDatabase 
Dim OraDynaset As OraDynaset 
Dim OraMetaData As OraMetaData 
Dim OraMDAttribute As OraMDAttribute 
Dim ColumnList As OraMetaData 
Dim Column As OraMetaData 
 
'Create the OraSession Object. 
Set OraSession = CreateObject("OracleInProcServer.XOraSession") 
 
'Create the OraDatabase Object by opening a connection to Oracle. 
Set OraDatabase = OraSession.OpenDatabase("ExampleDB", "scott/tiger", 0&) 
 
'Use Describe to retrieve the metadata object 
Set OraMetaData = OraDatabase.Describe("EMP") 
 
'Display the type of the metadata 
MsgBox TypeofMetaData & OraMetaData.Type 
 
'Display the count of attributes belonging to the table 
MsgBox NumberOfAttributes & OraMetaData.Count 
 
'Attribute can be accessed using the explicit OraMetaData property: Attribute  
'The index can be an integer or the attribute name 
Set OraMDAttribute = OraMetaData.Attribute(0) 
MsgBox "ObjectID: " & OraMDAttribute.Value 
 
'Since Attribute is the default property of OraMetaData, an attribute can
' be accessed as follows. Here, we use attribute name as an index 
Set OraMDAttribute = OraMetaData("ObjectID") 
MsgBox "Name: " & OraMDAttribute.Name 
MsgBox "Value: " & OraMDAttribute.Value 
 
'Value is the default property of OraMDAttribute, the following shows 
'the Value of property "IsClustered" for the table 
MsgBox "Is Clustered: " & OraMetaData!IsClustered 
MsgBox "Is Partitioned: " & OraMetaData!IsPartitioned 
 
'Retrieve the Column List 
Set OraMDAttribute = OraMetaData!ColumnList 
 
' Use IsMDObject property to check whether an attribute's value is an OraMetaData
If (OraMDAttribute.IsMDObject()) Then 
       Set ColumnList = OraMDAttribute.Value 
      'Display the name and data type of each column 
       For I = 0 To ColumnList.Count - 1 
        Set Column = ColumnList(I).Value 
 
' Each column is again an OraMetaData 
    MsgBox "Column: " & Column!Name & " data type: " & Column!Data Type 
  Next I 
End If

Example: Describing a User-Defined Type

Before running the following example, make sure that you have the necessary datatypes and tables in the database. See "Schema Objects Used in OraMetaData Examples".

Dim OraSession As OraSession 
Dim OraDatabase As OraDatabase 
Dim OraDynaset As OraDynaset 
Dim OraMetaData As OraMetaData 
Dim OraMDAttribute As OraMDAttribute 
Dim attrList As OraMetaData 
Dim attr As OraMetaData 
 
'Create the OraSession Object. 
Set OraSession = CreateObject("OracleInProcServer.XOraSession") 
 
'Create the OraDatabase Object by opening a connection to Oracle. 
Set OraDatabase = OraSession.OpenDatabase("ExampleDB", "scott/tiger",0&) 
Set OraMetaData = OraDatabase.Describe("ORAMD_ADDRESS") 
NumAttributes = OraMetaData!NumAttributes 
NumMethods = OraMetaData!NumMethods 
MsgBox "The Address type has " & NumAttributes & " attributes" 
MsgBox "Address Object has " & NumMethods & " methods" 
 
'Retrieve the attribute list of this type object 
Set attrList = OraMetaData!Attributes.Value 
 
'Display the name and data type of each attribute 
For I = 0 To attrList.Count - 1 
  Set attr = attrList(I).Value 
  ' each attr is actually an OraMetaData 
  MsgBox "Attribute Name: " & attr!Name 
  MsgBox "Attribute Type: " & attr!TypeName 
 
Next I

Example: Describing Unknown Schema Objects

Before running the following example, make sure that you have the necessary datatypes and tables in the database. See "Schema Objects Used in OraMetaData Examples".

Sub RecursiveDescribe(name$, xMD As OraMetaData) 
 
Dim xMDAttr As OraMDAttribute 
For I = 0 To xMD.Count - 1 
    Set xMDAttr = xMD.Attribute(I) 
 
    ' If an attribute can be described further, describe it, 
    ' otherwise display its attribute name & value 
    If (xMDAttr.IsMDObject) Then 
        RecursiveDescribe xMDAttr.name, xMDAttr.Value 
    Else 
        MsgBox name & "->" & xMDAttr.name & " = " & xMDAttr.Value 
  End If 
Next I 

End Sub 
Sub Main() 
 
'This example displays all the attributes of any schema object given 
Dim OraSession As OraSession 
Dim OraDatabase As OraDatabase 
Dim OraDynaset As OraDynaset 
Dim xMD As OraMetaData 
Dim x As String 
 
'Create the OraSession Object. 
Set OraSession = CreateObject("OracleInProcServer.XOraSession") 
 
'Create the OraDatabase Object by opening a connection to Oracle. 
Set OraDatabase = OraSession.OpenDatabase("ExampleDB", "scott/tiger", 0&) 
 
' x is any database object, here the EMP table is used as an example 
x = "EMP" 
Set xMD = OraDatabase.Describe(x) 
MsgBox x & " is of the type " & xMD.Type 
RecursiveDescribe x, xMD 

End Sub

See Also: