我正在尝试删除会话和与该会话相关的练习，使用:
$delete_session =
"DELETE FROM sessions, exercises
USING sessions
INNER JOIN exercises
ON sessions.session_id = exercises.session_id
WHERE sessions.session_id= '$delete_id'";
如果有练习链接到会话，上面的查询工作，但如果会话没有练习，则不触发。
我可以将上面的查询和下面的查询一起使用吗?
"DELETE FROM sessions WHERE session_id= '$delete_id'";
我怎么能得到会话将删除与它链接或没有练习?
应该使用LEFT INNER JOIN
$delete_session =
"DELETE FROM sessions, exercises
USING sessions
LEFT INNER JOIN exercises
ON sessions.session_id = exercises.session_id
WHERE sessions.session_id= '$delete_id'";