Proving SQL query equivalency

Question

How would you go about proving that two queries are functionally equivalent, eg they will always both return the same result set.

---

As I had a specific query in

Answer 1

This will do the trick. If this query returns zero rows the two queries are returning the same results. As a bonus, it runs as a single query, so you don't have to worry about setting the isolation level so that the data doesn't change between two queries.

select * from (( MINUS ) UNION ALL ( MINUS ))

Here's a handy shell script to do this:

#!/bin/sh

CONNSTR=$1
echo query 1, no semicolon, eof to end:; Q1=`cat` 
echo query 2, no semicolon, eof to end:; Q2=`cat`

T="(($Q1 MINUS $Q2) UNION ALL ($Q2 MINUS $Q1));"

echo select 'count(*)' from $T | sqlplus -S -L $CONNSTR