Use the MERGE statement when possible
Many developers are unaware, or afraid of the
powerful MERGE statement. Some databases know other forms of UPSERT statements, e.g. MySQL's ON DUPLICATE KEY UPDATE clause. But MERGE is really so powerful, most importantly in databases that heavily extend the SQL standard,
such as SQL Server.
The Cure:
If youre UPSERTING by chaining INSERT and UPDATE or by chaining SELECT .. FOR UPDATE and then INSERT or UPDATE, think again. Apart from risking race conditions, you might be able to express a simpler MERGE statement.
Source
SqlBestPractices 
