SQL - How to: IF then GO (execute new query) in the same script without dynamic SQL?

Question

In short, I'm managing a bunch of versioned SQL Scripts where one requirement is that they need to be sort of backwards compatible in that the same scripts can be executed multiple times, still guaranteeing the same end result for the latest version. Basically, say we are on version 3. We need to be able to run scripts for versions 1, 2 and 3 over and over, without errors, and still guarantee that the end result is the same complete version 3.

Now this is easy with normal scenarios (just check if column / table / type is right and create / modify if not), but how do you deal with for instance a trigger that's way over 8000 characters long and can't be executed as dynamic SQL? As version 2 is installed, the triggers are dropped, at the end, new ones are created to match v2's datamodel. But if v3 removed one of the columns referred to by the v2 trigger, that trigger will now fail.

I can't make any kind of IF checks to see if our log has v3 scripts, or if the datamodel doesn't match the requirements. I'd hate to make others do manual labor to do something I'm sure can be automated one way or another. So is there any nice gimmick, trick or just something I missed that could help?

Thanks for the help. :)

Answer 1

but how do you deal with for instance a trigger that's way over 8000 characters long and can't be executed as dynamic SQL?

It can be executed using sp_executesql for which size of sql statement is limited only by available database server memory.

You need to check if object exists and create it if you need or delete otherwise.

if object_id(N'your_table_name','U') is null
CREATE TABLE
...
GO
/* add column */
if not exists (select * from sys.columns
               where object_id=object_id('TableName','U') and name='ColumnName')
ALTER TABLE TableName
ADD ColumnName
GO
/* creating Stored Procedure */
if object_id(N'ProcedureName','P') is null
EXEC sp_executesql N'CREATE PROCEDURE ProcedureName AS print 1'
GO

ALTER PROCEDURE ProcedureName

AS
/*your actual code here*/
GO

/* and so on */

Object types for object_id function you can see here.