FETCH (Transact-SQL)

Artikkeli
02/28/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

Retrieves a specific row from a Transact-SQL server cursor.

Syntax

FETCH   
          [ [ NEXT | PRIOR | FIRST | LAST   
                    | ABSOLUTE { n | @nvar }   
                    | RELATIVE { n | @nvar }   
               ]   
               FROM   
          ]   
{ { [ GLOBAL ] cursor_name } | @cursor_variable_name }   
[ INTO @variable_name [ ,...n ] ]

Arguments

NEXT
Returns the result row immediately following the current row and increments the current row to the row returned. If FETCH NEXT is the first fetch against a cursor, it returns the first row in the result set. NEXT is the default cursor fetch option.

PRIOR
Returns the result row immediately preceding the current row, and decrements the current row to the row returned. If FETCH PRIOR is the first fetch against a cursor, no row is returned and the cursor is left positioned before the first row.

FIRST
Returns the first row in the cursor and makes it the current row.

LAST
Returns the last row in the cursor and makes it the current row.

ABSOLUTE { n| @nvar}
If n or @nvar is positive, returns the row n rows from the front of the cursor and makes the returned row the new current row. If n or @nvar is negative, returns the row n rows before the end of the cursor and makes the returned row the new current row. If n or @nvar is 0, no rows are returned. n must be an integer constant and @nvar must be smallint, tinyint, or int.

RELATIVE { n| @nvar}
If n or @nvar is positive, returns the row n rows beyond the current row and makes the returned row the new current row. If n or @nvar is negative, returns the row n rows prior to the current row and makes the returned row the new current row. If n or @nvar is 0, returns the current row. If FETCH RELATIVE is specified with n or @nvar set to negative numbers or 0 on the first fetch done against a cursor, no rows are returned. n must be an integer constant and @nvar must be smallint, tinyint, or int.

GLOBAL
Specifies that cursor_name refers to a global cursor.

cursor_name
Is the name of the open cursor from which the fetch should be made. If both a global and a local cursor exist with cursor_name as their name, cursor_name to the global cursor if GLOBAL is specified and to the local cursor if GLOBAL is not specified.

@cursor_variable_name
Is the name of a cursor variable referencing the open cursor from which the fetch should be made.

INTO @variable_name[ ,...n]
Allows data from the columns of a fetch to be placed into local variables. Each variable in the list, from left to right, is associated with the corresponding column in the cursor result set. The data type of each variable must either match or be a supported implicit conversion of the data type of the corresponding result set column. The number of variables must match the number of columns in the cursor select list.

Remarks

If the SCROLL option is not specified in an ISO style DECLARE CURSOR statement, NEXT is the only FETCH option supported. If SCROLL is specified in an ISO style DECLARE CURSOR, all FETCH options are supported.

When the Transact-SQL DECLARE cursor extensions are used, these rules apply:

If either FORWARD_ONLY or FAST_FORWARD is specified, NEXT is the only FETCH option supported.
If DYNAMIC, FORWARD_ONLY or FAST_FORWARD are not specified, and one of KEYSET, STATIC, or SCROLL are specified, all FETCH options are supported.
DYNAMIC SCROLL cursors support all the FETCH options except ABSOLUTE.

The @@FETCH_STATUS function reports the status of the last FETCH statement. The same information is recorded in the fetch_status column in the cursor returned by sp_describe_cursor. This status information should be used to determine the validity of the data returned by a FETCH statement prior to attempting any operation against that data. For more information, see @@FETCH_STATUS (Transact-SQL).

Permissions

Permissions for FETCH default to any valid user.

Examples

A. Using FETCH in a simple cursor

The following example declares a simple cursor for the rows in the Person.Person table with a last name that starts with B, and uses FETCH NEXT to step through the rows. The FETCH statements return the value for the column specified in DECLARE CURSOR as a single-row result set.

USE AdventureWorks2022;  
GO  
DECLARE contact_cursor CURSOR FOR  
SELECT LastName FROM Person.Person  
WHERE LastName LIKE 'B%'  
ORDER BY LastName;  
  
OPEN contact_cursor;  
  
-- Perform the first fetch.  
FETCH NEXT FROM contact_cursor;  
  
-- Check @@FETCH_STATUS to see if there are any more rows to fetch.  
WHILE @@FETCH_STATUS = 0  
BEGIN  
   -- This is executed as long as the previous fetch succeeds.  
   FETCH NEXT FROM contact_cursor;  
END  
  
CLOSE contact_cursor;  
DEALLOCATE contact_cursor;  
GO

B. Using FETCH to store values in variables

The following example is similar to example A, except the output of the FETCH statements is stored in local variables instead of being returned directly to the client. The PRINT statement combines the variables into a single string and returns them to the client.

USE AdventureWorks2022;  
GO  
-- Declare the variables to store the values returned by FETCH.  
DECLARE @LastName VARCHAR(50), @FirstName VARCHAR(50);  
  
DECLARE contact_cursor CURSOR FOR  
SELECT LastName, FirstName FROM Person.Person  
WHERE LastName LIKE 'B%'  
ORDER BY LastName, FirstName;  
  
OPEN contact_cursor;  
  
-- Perform the first fetch and store the values in variables.  
-- Note: The variables are in the same order as the columns  
-- in the SELECT statement.   
  
FETCH NEXT FROM contact_cursor  
INTO @LastName, @FirstName;  
  
-- Check @@FETCH_STATUS to see if there are any more rows to fetch.  
WHILE @@FETCH_STATUS = 0  
BEGIN  
  
   -- Concatenate and display the current values in the variables.  
   PRINT 'Contact Name: ' + @FirstName + ' ' +  @LastName  
  
   -- This is executed as long as the previous fetch succeeds.  
   FETCH NEXT FROM contact_cursor  
   INTO @LastName, @FirstName;  
END  
  
CLOSE contact_cursor;  
DEALLOCATE contact_cursor;  
GO

C. Declaring a SCROLL cursor and using the other FETCH options

The following example creates a SCROLL cursor to allow full scrolling capabilities through the LAST, PRIOR, RELATIVE, and ABSOLUTE options.

USE AdventureWorks2022;  
GO  
-- Execute the SELECT statement alone to show the   
-- full result set that is used by the cursor.  
SELECT LastName, FirstName FROM Person.Person  
ORDER BY LastName, FirstName;  
  
-- Declare the cursor.  
DECLARE contact_cursor SCROLL CURSOR FOR  
SELECT LastName, FirstName FROM Person.Person  
ORDER BY LastName, FirstName;  
  
OPEN contact_cursor;  
  
-- Fetch the last row in the cursor.  
FETCH LAST FROM contact_cursor;  
  
-- Fetch the row immediately prior to the current row in the cursor.  
FETCH PRIOR FROM contact_cursor;  
  
-- Fetch the second row in the cursor.  
FETCH ABSOLUTE 2 FROM contact_cursor;  
  
-- Fetch the row that is three rows after the current row.  
FETCH RELATIVE 3 FROM contact_cursor;  
  
-- Fetch the row that is two rows prior to the current row.  
FETCH RELATIVE -2 FROM contact_cursor;  
  
CLOSE contact_cursor;  
DEALLOCATE contact_cursor;  
GO

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