SQL Server compare results of two queries that should be identical

Question

I am modifying a sql server 2005 stored procedure slightly for performance, and I would like to quickly make sure the old stored proc and the new one return the exact same r

Answer 1

To complete @jabs answer, you can use the following template to get the difference between two queries:

WITH q1 AS ()
   , q2 AS ()
SELECT * FROM q1 EXCEPT SELECT * FROM q2
UNION ALL (
SELECT * FROM q2 EXCEPT SELECT * FROM q1);

---

Example 1: This returns 0 rows, as the queries are identical

WITH q1 AS (SELECT * FROM my_table)
   , q2 AS (SELECT * FROM my_table)
SELECT * FROM q1 EXCEPT SELECT * FROM q2
UNION ALL (
SELECT * FROM q2 EXCEPT SELECT * FROM q1);

Example 2: This returns the different rows between the queries (where foo = 'bar')

WITH q1 AS (SELECT * FROM my_table)
   , q2 AS (SELECT * FROM my_table WHERE foo <> 'bar')
SELECT * FROM q1 EXCEPT SELECT * FROM q2
UNION ALL (
SELECT * FROM q2 EXCEPT SELECT * FROM q1);

Example 3: Just for fun, you can check that the query in Example 2 is identical to queries the rows where foo = 'bar'.

WITH q1 AS (

    WITH q1 AS (SELECT * FROM my_table)
       , q2 AS (SELECT * FROM my_table WHERE foo <> 'bar')
    SELECT * FROM q1 EXCEPT SELECT * FROM q2
    UNION ALL (
    SELECT * FROM q2 EXCEPT SELECT * FROM q1)

)
   , q2 AS (SELECT * FROM my_table WHERE foo = 'bar')
SELECT * FROM q1 EXCEPT SELECT * FROM q2
UNION ALL (
SELECT * FROM q2 EXCEPT SELECT * FROM q1);