There are mutliple ways to do that,
1) The easiest way is to use database tool such as SQL Developer or TOAD and execute and test the query there.
2)If you don't have these tools and you have admin privilege in OBIEE you can look for Direct database request(OBIEE)
3)If you do not have access direct db request you can write the logical sql in advanced tab of criteria and execute the report. Which is the most helpful and easiest method to execute your own queries. ( It is very simple once you are familiar with it)
Kindly mark correct/helpful if it helped you