Question

I have written a complex stored procedure that moves records between several tables based on complex logic. I have checked each little piece of the logic carefully but I want to have maximal confidence in the code. Is there a way to declare a logical relationship that must hold between the beginning and end of the SP? If these conditions are not met, I imagine that the SP will be rolled back.

Specifically, I want to declare that records in table A that are picked out by a set of logical conditions will be in table B (and not in table A) at the end of the SP and that records not picked out by those set of logical conditions will still be in table X at the end of the SP. I use a boolean function to pick out the records in A that match the conditions.

I know that I can test some of these things with nUnit but I am wondering if there is a way to declare and enforce this sort of logic within t-SQL itself.

Answer 1

If your records have a field containing a unique ID you can do a simple INSERT + SELECT from TableA into TableB and then a simple DELETE of the inserted original records.

For instance first insert all the records matching your selection criteria into TableB:

INSERT INTO TableB (uniqueID, Field1, Field2, FieldN)
SELECT uniqueID,
       Field1,
       Field2,
       FieldN
FROM   TableA
WHERE  FieldN = SomeCriteria

And then delete from TableA all the records you just inserted into tableB using the field uniqueID as the selction criteria to determine which records to delete:

DELETE TableA
WHERE  uniqueID IN (SELECT uniqueID
                    FROM   TableB)

If you put both statements in a single transaction with a couple error checks you should be protected in case something goes wrong while the two statements are executing:

BEGIN TRANSACTION

INSERT INTO TableB (uniqueID, Field1, Field2, FieldN)
SELECT uniqueID,
       Field1,
       Field2,
       FieldN
FROM   TableA
WHERE  FieldN = SomeCriteria;

IF @@ERROR <> 0 THEN
BEGIN
    ROLLBACK TRANSACTION
    RETURN (@@ERROR)
END

DELETE TableA
WHERE  uniqueID IN (SELECT uniqueID
                    FROM   TableB);
if @@ERROR <> 0 THEN
BEGIN
    ROLLBACK TRANSACTION
    RETURN (@@ERROR)
END

COMMIT TRANSACTION 

If you do not have a single column which can unique identify each of your records you can use EXISTS instead of IN for selecting the records to DELETE from TableA:

DELETE TableA
WHERE  EXISTS (SELECT *
               FROM   TableB
               WHERE  TableA.field1 = TableB.field1
                      AND TableA.field2 = TableB.field2
                      AND TableA.FieldN = TableB.fieldn);