SQL Server transaction with custom template - sql

Question

I would ask a basilar thing, I would use the native transaction stuffs to rollback a bunch of tables if some conditions are verified.
I really have to check how many updates results based of some stored procedure that gather data from tables populated by input reports, too less changes or too many changes means rollback because we will reject the reports. I would implements this feature with the native transaction of T-SQL, this is a pseudo of my idea:
CREATE PROCEDURE mytest
AS
BEGIN
BEGIN TRANSACTION
BEGIN TRY
EXEC foo
EXEC bar
EXEC baz
END TRY
IF true
COMMIT TRANSACTION
ELSE
ROLLBACK TRANSACTION
END
Of course, this is not working because of incorrect syntax near the keyword 'IF', maybe because it's not the right way to use transaction.
Fixed this I will think how to count the changes of a table, if need to use a temporary table or if I can use some SQL features. I'm search for docs or example but I'm, not finding anything.
Any hints?

Answer 1

Your pseudo-code is missing a catch block. Below is an example that includes the error handling and other improvements.
CREATE PROCEDURE mytest
AS
SET XACT_ABORT ON; --best practice with explict transactions in procs
BEGIN TRY
BEGIN TRAN;
EXEC foo;
EXEC bar;
EXEC baz;
IF (<your-validation-succeeded-condition-here>)
COMMIT;
ELSE
ROLLBACK;
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0 ROLLBACK;
THROW;
END CATCH;

Answer 2

The problem, as I mention in the comment, isn't the IF...ELSE it's that you have no CATCH. A TRY...CATCH requires both a TRY and a CATCH; unlike an IF...ELSE which can only have an IF.
You likely, therefore, want something like this:
CREATE PROCEDURE dbo.MyTest AS
BEGIN
SET NOCOUNT ON;
BEGIN TRANSACTION MyTransaction;
BEGIN TRY
EXEC FOO;
EXEC BAR;
EXEC BAZ;
IF {Your Boolean Expression}
COMMIT TRANSACTION MyTransaction;
ELSE
ROLLBACK TRANSACTION MyTransaction;
END TRY
BEGIN CATCH
ROLLBACK TRANSACTION MyTransaction;
THROW;
END CATCH;
END;