Hello New1, I'm not a QA nor an IT pro, I'm running for presidency this year, I'm gonna make America great again I'll deport illegals and punish abortion. Well I guess its to late to make you April fool, Cheer up!! I see few illegal aliens here are making you confused. To the point:
SQL based testing jobs are pretty easy, all you need to know is basic SQL concept.. once you know how to run queries and get the result set.. finding bugs is pretty easy. Make a test plan see If the SQL statement is running or not thats mostly the testing job all you will require to do however it might be wider than imagination but its good enough to start some where. As far as the assessment is concerned if you work on your SQL for 5 days you are good to go. Just be confident. Here is the link to 50 popular SQL interview question for testers:
http://www.softwaretestinghelp.com/50-popular-sql-interview-questions-for-testers/