While checking SQL syntax itself is somewhat straightforward, [Joe]’s sql-lint tool will also check the semantics of it by looking up the actual database and performing sanity checks on it.

FROM statement using source data that's known to have flaws. Back to the OP - either filter out the bad records in the WHERE clause, or put a CASE statement in the UPDATE list. No need for a cursor.

Learn how to master the SELECT statement to form truly useful data queries. This article explains functions, clauses, and keywords that will make your life a lot easier.