Mysql merging two queries into one

Question

Trying to merge below two queries into one in the most "correct/efficient" way:

select id from TABLE1 where apple='green'
while{
select * from TABLE2 where id=[id from TABLE1 above]
while{

Eg query one will return a number of id's which in turn will return a number of rows in query two.

Answer 1

You can try to use EXISTS subquery

SELECT * 
FROM TABLE2 t2
WHERE EXISTS(
    SELECT 1 
    FROM TABLE1 t1
    WHERE t1.apple='green' AND t1.id = t2.id
)