SQL update from one Table to another based on a ID match

Question

I have a database with account numbers and card numbers. I match these to a file to update any card numbers to the account number, so

Answer 1

This will allow you to update a table based on the column value not being found in another table.

    UPDATE table1 SET table1.column = 'some_new_val' WHERE table1.id IN (
            SELECT * 
            FROM (
                    SELECT table1.id
                    FROM  table1 
                    LEFT JOIN table2 ON ( table2.column = table1.column ) 
                    WHERE table1.column = 'some_expected_val'
                    AND table12.column IS NULL
            ) AS Xalias
    )

This will update a table based on the column value being found in both tables.

    UPDATE table1 SET table1.column = 'some_new_val' WHERE table1.id IN (
            SELECT * 
            FROM (
                    SELECT table1.id
                    FROM  table1 
                    JOIN table2 ON ( table2.column = table1.column ) 
                    WHERE table1.column = 'some_expected_val'
            ) AS Xalias
    )