一个mysql操作中的三个WHERE语句可以作为更好的过滤器吗？

Question

I'm trying to compare two tables and work on a result of this operation.

SELECT * FROM table1
WHERE table1.czlowiek_id NOT IN (
    SELECT table2.czlowiek_id
    FROM table2
    WHERE table1.czlowiek_id=table2.czlowiek_id
)  
OR table1.czlowiek_id IN (
    SELECT table2.czlowiek_id
    FROM table2
    WHERE table1.czlowiek_id=table2.czlowiek_id
    AND table2.szkolenie_id IN ('$selected_one')
    AND table1.instruktor IN ('$selected_two')
) 

Is there some option to work on a result from this query adding another WHERE statement?

Answer 1

You may be able to solve the problem with a LEFT JOIN. This will allow you to pull all of the results from table1 that don't exist in table2, AND pull the results from table1 that are in table2 and match the requested filters.

SELECT
    *
FROM
    table1
    LEFT JOIN table2 ON table1.czlowiek_id=table2.czlowiek_id
WHERE
    table2.czlowiek_id IS NULL
    OR (
        table2.szkolenie_id IN ('$selected_one')
        AND table1.instruktor IN ('$selected_two')
    )