问是否可以在另一条SELECT语句中使用SELECT语句的结果？

EN

SELECT * FROM BlockUsers
WHERE OwnerID IN (SELECT ID FROM UserAccounts WHERE.....)
              ^^--- use 'in' instead of '=';

SELECT * FROM BlockUsers
WHERE OwnerID IN
(SELECT ID FROM UserAccounts WHERE Code='$UserCode')
AND
BlockID IN
(SELECT ID FROM UserAccounts WHERE Code='$BlockUserCode')
LIMIT 1

SELECT * FROM BlockUsers AS bu
INNER JOIN UserAccounts AS ua1 ON ua1.ID = bu.OwnerID
INNER JOIN UserAccounts AS ua2 ON ua2.ID = bu.BlockID
WHERE ua1.Code = '$UserCode' AND ua2.Code = '$BlockUserCode'
LIMIT 1

SELECT BlockUsers.* FROM BlockUsers
JOIN UserAccounts as UA1 ON Code='$UserCode' AND OwnerID = UA1.ID
JOIN UserAccounts as UA2 ON Code='$BlockUserCode' AND BlockID = UA2.ID
LIMIT 1