Insert or Update Approaches in SQL Server

Recently I needed to write a stored procedure that would update a row if it existed in a queue table, and if it did not then to insert the row. Thinking from a pseudo code thought process, you’d run a “IF EXISTS (SELECT Id FROM TABLE) UPDATE, ELSE INSERT INTO TABLE..” Whilst this approach does work, it would be inefficient. This will do a table/index scan twice: once for the SELECT statement and the UPDATE statement.

Depending on your version of SQL Server, there are more efficient ways to do this: