Result not the same while using select statement and table-valued function T-SQL

Question

My ORDER BY clause works differently. If I am using a SELECT statement with ORDER BY everything is fine, all is sorted as i want.

But if I use TABLE-VALUED FUNCTION with the exact same SELECT statement inside that function it doesn't sort properly.

To clarify:

That works 100% as it should.

DECLARE
@Number1_min as int = 1
@Number1_max as int = 100
@Number2_min as int = 1
@Number2_max as int = 100

SELECT ROW_NUMBER() over (order by Number1) LP,
Number1,
Number2

FROM TABLE1

WHERE
Number1>=@Number1_min and
Number1<=@Number1_max and
Number2>=@Number2_min and
Number2<=@Number2_max
ORDER BY LP

That version doesn't sort properly. When I put that SELECT into a TABLE-VALUED FUNCTION it works only with a small number of result. If I recive not so many rows as a result, for example 30 rows, it works as it should and in a good order. The problem is when i recive something like 4000 rows of result it is not sorted properly.

CREATE FUNCTION [dbo].[Numbers]
(
@Number1_min int
@Number1_max int
@Number2_min int
@Number2_max int
)

RETURNS 
@Table_Var TABLE 
(
LP int,
Number1 int,
Number2 int
)
AS
BEGIN

    Insert @Table_Var
    (
    LP,Number1,Number2
    )

SELECT ROW_NUMBER() over (order by Number1) LP,
Number1,
Number2

FROM TABLE1

WHERE
Number1>=@Number1_min and
Number1<=@Number1_max and
Number2>=@Number2_min and
Number2<=@Number2_max

ORDER BY LP
RETURN
END

In both ways i recieve the same number of rows and the same data. The only difference is that when I am trying to use TABLE-VALUED FUNCTION it sorts parts of a result. For example that SELECT returns 5350 rows. Using a FUNTCTION I don't recive ORDERED BY from 1 to 5350, but something like 1-336 next 1365-1701, ... , 1026-1364, etc. The result is that i recieve all of those 5350 rows, but not ordered properly.

The key is that I would like to recieve good order just by calling this function, so I don't want any ordering of a function's result.

EDIT: I have found out, when WHERE clause is commented in TABLE_VALUED FUNCTION everything works fine. So the question is:

"Why does WHERE statement destroys an ORDER BY statement?"

score 0 · Answer 1 · answered Nov 25 '22 at 08:25

SQL Server might choose to ignore the order by based on the optimization and query plan.

It is not easy to fully understand all the decisions the query engine is making, but for some reason, SQL Server query engine chooses to ignore the order by when the query is using the where. I could take a wild guess that SQL Server query engine sees the order by as misplaced, as it is not normal to place order by like that. e.g. you cannot place an order by in a view.

You should instead apply the order by when you call the table function, that will work all the time, and that is also where order by clauses makes most sense, and it will allow you to do asc or desc order by. An alternative is to sort on the client side.

Result not the same while using select statement and table-valued function T-SQL

1 Answers1