When Should You Use Table Variables?

Screech


Links:

USE StackOverflow2013;
EXEC dbo.DropIndexes;
SET NOCOUNT ON;
DBCC FREEPROCCACHE;
GO 

CREATE INDEX whatever 
ON dbo.Posts
    (OwnerUserId) 
INCLUDE
    (Score);
GO 

CREATE OR ALTER PROCEDURE dbo.TempTableTest (@Id INT)
AS
BEGIN
SET NOCOUNT, XACT_ABORT ON;
    
    CREATE TABLE #t(i INT NOT NULL);

    INSERT 
        #t ( i )
    SELECT 
        p.Score
    FROM dbo.Posts AS p
    WHERE p.OwnerUserId = @Id;

END;
GO 

CREATE OR ALTER PROCEDURE dbo.TableVariableTest (@Id INT)
AS
BEGIN
SET NOCOUNT, XACT_ABORT ON;
    
    DECLARE @t TABLE (i INT NOT NULL);

    INSERT 
        @t ( i )
    SELECT 
        p.Score
    FROM dbo.Posts AS p
    WHERE p.OwnerUserId = @Id;

END;
GO 


CREATE OR ALTER PROCEDURE dbo.TempTestWrapper (@TestProc sysname)
AS
BEGIN
SET NOCOUNT, XACT_ABORT ON;

DECLARE @rando int = 
    ((ABS(CHECKSUM(NEWID())) % 21195018) + 1); /*this is the max id in posts for SO2013*/

IF @TestProc = N'TempTableTest'
    BEGIN
        EXEC dbo.TempTableTest @rando;
    END;

IF @TestProc = N'TableVariableTest'
    BEGIN
        EXEC dbo.TableVariableTest @rando;
    END;

END;
GO 

/*Testing*/
EXEC dbo.TempTestWrapper @TestProc = 'TempTableTest';
EXEC dbo.TempTestWrapper @TestProc = 'TableVariableTest';

/*

ostress -SSQL2019S -d"StackOverflow2013" -Q"EXEC dbo.TempTestWrapper @TestProc = 'TempTableTest';" -U"ostress" -P"ostress" -q -n300 -r1000 -o"C:\temp\crap"

ostress -SSQL2019S -d"StackOverflow2013" -Q"EXEC dbo.TempTestWrapper @TestProc = 'TableVariableTest';" -U"ostress" -P"ostress" -q -n300 -r1000 -o"C:\temp\crap"

*/


2 thoughts on “When Should You Use Table Variables?

  1. I’ll just leave two additional use cases for table variables: they hold the inserted values after a rollback and, if you care about localization (for whatever reason, just as an example, your database has a different collation than your default sql installation), then the only way to go is via table variables.

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