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Message Schemas for REF CURSORS

  • Artigo

A REF CURSOR is an Oracle PL/SQL data type that represents a pointer to a result set in the Oracle database. REF CURSOR types enable input and output streaming of data and are ideal for transferring large amounts of data to and from a PL/SQL code block. Microsoft BizTalk Adapter for Oracle Database provides support for passing strongly-typed and weakly-typed REF CURSOR parameters to PL/SQL procedures and functions as IN, OUT and IN OUT parameters.

In the Oracle database, a REF CURSOR type can be either strongly-typed or weakly-typed:

  • A strongly-typed REF CURSOR is declared with a RETURN clause as in TYPE StrongCurType IS REF CURSOR RETURN emp%ROWTYPE;. A strongly-typed REF CURSOR variable can only represent a result set that contains data that matches the type with which its REF CURSOR type is declared. The Oracle Database adapter returns a strongly-typed result set for a strongly-typed REF CURSOR.

  • A weakly-typed REF CURSOR is declared without a RETURN clause as in TYPE WeakCurType IS REF CURSOR;. Oracle also provides a special REF CURSOR type called SYS_REFCURSOR that can be used to declare weakly-typed REF CURSOR variables. Weakly-typed REF CURSOR variables can represent a result set that contains any kind of row data. The Oracle Database adapter returns a weakly-typed result set of generic records for a weakly-typed REF CURSOR.

IN REF CURSOR Parameters

There is no ODP.NET API to create a REF CURSOR on the Oracle server, so the Oracle Database adapter cannot provide the capability for a client program to create and maintain REF CURSOR variables.

The Oracle Database adapter does, however, enable a client to pass IN REF CURSOR parameters to functions or stored procedures by specifying a block of PL/SQL code that returns a REF CURSOR. The adapter uses this code to create and OPEN a REF CURSOR variable on the Oracle server; it then calls the function or stored procedure using this variable as the IN parameter.

The Oracle Database adapter represents IN REF CURSOR parameters as strings that contain the PL/SQL code block. Within this block, the location of the REF CURSOR is specified with a question mark (?). The PL/SQL code block can contain an OPEN-FOR statement that contains a SQL query; or it can contain a function or procedure call in which an opened REF CURSOR is returned in an OUT parameter.

The following shows how to specify an IN REF CURSOR by calling a stored procedure or function to open the REF CURSOR.

<[IN_REF_CURSOR_PARAM_NAME]>begin [SP_NAME]([SP_PARAMS...], ?, [SP_PARAMS...]); end;</[IN_REF_CURSOR_PARAM_NAME]>  
  
Example:  
<EMP_RC>begin GETEMP(1, ?); end; </EMP_RC>

The following shows how to specify an IN REF CURSOR by using a SELECT query to open the REF CURSOR.

<IN_REF_CURSOR_PARAM_NAME>begin open ? for select [FIELD_NAMES] from [TABLE_NAME]; end;</IN_REF_CURSOR_PARAM_NAME>  
  
Example:  
<EMP_RC>begin open ? for select * from EMP; end;</EMP_RC>

OUT REF CURSOR Parameters

OUT REF CURSOR parameters are returned as either strongly-typed or weakly-typed result sets. The type of the result set returned depends on whether the REF CURSOR parameter is declared as a strongly-typed or weakly-typed REF CURSOR in the stored procedure or function definition on the Oracle server. A strongly-typed result set is returned for strongly-typed REF CURSOR parameters and a weakly-typed result set is returned for weakly-typed REF CURSOR parameters (for example, parameters declared with a SYS_REFCURSOR type).

The following shows the XML for a strongly-typed OUT REF CURSOR parameter.

<[PARAM_NAME]>  
 <[PARAM_NAME]RECORD>  
  <[COL1_NAME]>value1</[COL1_NAME]>  
  <[COL2_NAME]>value2</[COL2_NAME]>  
  ...  
 </[PARAM_NAME]RECORD>  
</[PARAM_NAME]>  
  
[PARAM_NAME] = OUT REF CURSOR parameter name; for example, EMP_REFCURSOR  
[COL_NAME] = Name of a column in the REF CURSOR type; for example, Name.

The following shows the XML for a weakly-typed OUT REF CURSOR parameter.

<[PARAM_NAME]>  
 <GenRecordRow xmlns="oracledb">  
  <GenRecordColumn>  
   <ColumnName>COL_NAME</ColumnName>  
   <ColumnValue>COL_VALUE</ColumnValue>  
   <ColumnType>COL_TYPE</ColumnType>  
  </GenRecordColumn>  
  …  
 </GenRecordRow>  
 …  
</[PARAM_NAME]>  
  
[COL_NAME] = Name of column; for example, Name  
[COL_VALUE] = Column value; for example, Scott  
[COL_TYPE] = Column data type; for example, System.String

IN OUT REF CURSOR Parameters

Because the Oracle Database adapter models IN REF CURSOR parameters as strings and OUT REF CURSOR parameters as complex types, it cannot support a single type for an IN OUT REF CURSOR parameter. For this reason, it treats IN OUT REF CURSOR parameters as two different parameters: an IN parameter in the request message and an OUT parameter in the response message.

To avoid a name conflict in service model programming, the Oracle Database adapter appends the string "_IN" to the IN parameter in the request message so that for a given parameter named [PARAM_NAME], two parameters are created:

  • [PARAM_NAME]_IN is an IN REF CURSOR parameter in the stored procedure or function request message. It contains a PL/SQL statement (either a select query or a stored procedure or function call) that returns a REF CURSOR.

  • [PARAM_NAME] is an OUT REF CURSOR parameter in the stored procedure or function response message. It contains the OUT REF CURSOR as a strongly-typed or weakly-typed result set.

Important

The adapter cannot support a procedure or function that contains an IN parameter named [PARAM_NAME]_IN and an IN OUT REF CURSOR parameter named [PARAM_NAME]. This is because the adapter expects a parameter named [PARAM_NAME]_IN to represent the input to the REF CURSOR parameter, and you cannot specify both parameters in the request message.

See Also

Messages and Message Schemas for BizTalk Adapter for Oracle Database