Megosztás a következőn keresztül:

  • Cikk

Using the cursor Data Type in an OUTPUT Parameter

Transact-SQL stored procedures can use the cursor data type only for OUTPUT parameters. If the cursor data type is specified for a parameter, both the VARYING and OUTPUT parameters are required. If the VARYING keyword is specified for a parameter, the data type must be cursor and the OUTPUT keyword must be specified.

Note

The cursor data type cannot be bound to application variables through the database APIs such as OLE DB, ODBC, ADO, and DB-Library. Because OUTPUT parameters must be bound before an application can execute a stored procedure, stored procedures with cursor OUTPUT parameters cannot be called from the database APIs. These procedures can be called from Transact-SQL batches, stored procedures, or triggers only when the cursor OUTPUT variable is assigned to a Transact-SQL local cursor variable.

Cursor Output Parameters

The following rules pertain to cursor output parameters when the procedure is executed:

  • For a forward-only cursor, the rows returned in the cursor's result set are only those rows at and beyond the position of the cursor at the conclusion of the stored procedure executed, for example:

    • A nonscrollable cursor is opened in a procedure on a result set named RS of 100 rows.

    • The procedure fetches the first 5 rows of result set RS.

    • The procedure returns to its caller.

    • The result set RS returned to the caller consists of rows from 6 through 100 of RS, and the cursor in the caller is positioned before the first row of RS.

  • For a forward-only cursor, if the cursor is positioned before the first row upon completion of the stored procedure, the entire result set is returned to the calling batch, stored procedure, or trigger. When returned, the cursor position is set before the first row.

  • For a forward-only cursor, if the cursor is positioned beyond the end of the last row upon completion of the stored procedure, an empty result set is returned to the calling batch, stored procedure, or trigger.

    Note

    An empty result set is not the same as a null value.

  • For a scrollable cursor, all the rows in the result set are returned to the calling batch, stored procedure, or trigger at the conclusion of the execution of the stored procedure. When returned, the cursor position is left at the position of the last fetch executed in the procedure.

  • For any type of cursor, if the cursor is closed, then a null value is passed back to the calling batch, stored procedure, or trigger. This will also be the case if a cursor is assigned to a parameter, but that cursor is never opened.

    Note

    The closed state matters only at return time. For example, it is valid to close a cursor part of the way through the procedure, to open it again later in the procedure, and return that cursor's result set to the calling batch, stored procedure, or trigger.

Example

In the following example, a stored procedure is created that specified an output parameter, @currency\_cursor using the cursor data type. The stored procedure is then called in a batch

First, create the procedure that declares and then opens a cursor on the Currency table.

USE AdventureWorks;
GO
IF OBJECT_ID ( 'dbo.uspCurrencyCursor', 'P' ) IS NOT NULL
    DROP PROCEDURE dbo.uspCurrencyCursor;
GO
CREATE PROCEDURE dbo.uspCurrencyCursor 
    @CurrencyCursor CURSOR VARYING OUTPUT
AS
    SET NOCOUNT ON;
    SET @CurrencyCursor = CURSOR
    FORWARD_ONLY STATIC FOR
      SELECT CurrencyCode, Name
      FROM Sales.Currency;
    OPEN @CurrencyCursor;
GO

Next, execute a batch that declares a local cursor variable, executes the procedure to assign the cursor to the local variable, and then fetches the rows from the cursor.

USE AdventureWorks;
GO
DECLARE @MyCursor CURSOR;
EXEC dbo.uspCurrencyCursor @CurrencyCursor = @MyCursor OUTPUT;
WHILE (@@FETCH_STATUS = 0)
BEGIN;
     FETCH NEXT FROM @MyCursor;
END;
CLOSE @MyCursor;
DEALLOCATE @MyCursor;
GO