MySQL optimized query for not in

Question

I have an excel with VBA program which connects to MySQL database to retrieve some information. Initially, when the program loads I have the below query.

SELECT          


        

Answer 1

Use an outer join

SELECT A.*
FROM Table1 a
LEFT OUTER JOIN (SELECT DISTINCT subject
            FROM Table2) b ON a.id = b.subject
WHERE b.subject IS NULL

Answer 2

Query:

SELECT a.*
FROM Table1 a
WHERE NOT EXISTS (SELECT subject
                  FROM Table2 b
                  WHERE a.id = b.subject)

Answer 3

Similar to the other offered answer, however the query may perform better with a direct link to the table rather than to an inline view on a SELECT DISTINCT:

SELECT t1.*
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.id = t2.subject
WHERE t2.subject IS NULL