Question

I’m writing a stored procedure to update multiple records based on a table variable parameter.

The existing table is: Tb_Project_Image with relevant columns:

id PK (identity 1,1) 
cat_ord decimal(4,2)

The procedure will receive a temporary table variable (shown in the code below) containing the id as PI_ID, and the new value for cat_ord as newCatOrd. idx is a simple identity for each row containing 1…n where n is the rowcount of @tempTable.

For each row in @tempTable, I want to update Tb_Project_Image where id = PI_ID to the corresponding value.

    DECLARE @tempTable table (
    idx smallint Primary Key IDENTITY(1,1),
    PI_ID bigint, 
    newCatOrd decimal(4, 2) not null )

    INSERT INTO @tempTable values (3, 7.01)
    INSERT INTO @tempTable values (4, 7.02)
    INSERT INTO @tempTable values (5, 7.03)
    --etc...
    DECLARE @error int
    DECLARE @update int
    DECLARE @iter int
    SET @iter = 1

    BEGIN TRAN
WHILE @iter <= (select COUNT(*) from @tempTable)
    BEGIN
        UPDATE Tb_Project_Image
        SET cat_ord = (SELECT newCatOrd FROM @tempTable 
                        WHERE idx = @iter)
        WHERE id = (SELECT PI_ID FROM @tempTable
                        WHERE idx = @iter)  
        --error checking            
        set @error = @@ERROR
        set @update = @@ROWCOUNT
        IF ((@error = 0) AND (@update = 1))
            BEGIN
            SET @iter = @iter + 1
            CONTINUE
            END
        ELSE
            BREAK
    END

IF ((@error = 0) AND (@update = 1)) 
    COMMIT TRAN
ELSE
    ROLLBACK TRAN
GO

Now, the error checking is because, to ensure integrity, EACH row in the temporary table MUST make 1 update. (explanation omitted to save space) If a single iteration of the while loop threw an error, or didn’t effect exactly 1 row, I want to break the loop and rollback the transaction

THE PROBLEM I’m having is that this error checking is not working. I’m currently running it with 14 rows in @tempTable and the 11th uses a PI_ID not found in the Project_Image table. Therefore, @update = 0... but it continues the loop and commits the data.

I’d be doubly glad if someone had a method of doing this that only used a single update statement.

Answer 1

You cannot do it this way, because even SET resets the state of @@ERROR and @@ROWNUMBER variables. In this case @@ROWCOUNT is set to 1 after set @error = @@ERROR. If you do not assign the values to local variables, your code will work:

IF ((@@error = 0) AND (@@rowcount = 1))

But you might rather try try…catch error handling and test @@rowcount separately after update.

UPDATE: doing it in single update:

UPDATE t
   SET cat_ord = tt.newCatOrd
  FROM Tb_Project_Image t
 INNER JOIN @tempTable tt
    ON t.id = tt.PI_ID
-- If there was PI_ID not found in Tb_Project_Image
-- But I think that this should have been dealt with
-- During the initial loading of temporary table
IF @@ROWCOUNT <> (select count (*) from @tempTable)
BEGIN
   -- Error reporting here
   ROLLBACK TRANSACTION
END