[英]How To Left Join A Table Based On The Value Received From Inner Join Of The Same Query
我试图运行以下查询,并不断收到语法错误。 没有LEFT JOIN,查询工作正常。 如何实现LEFT JOIN而不出错?
SELECT
m.mid,
m.seq,
m.created_on,
m.created_by,
m.body,
r.status,
u.username_clean
FROM message_recipient r
INNER JOIN message m
ON m.mid = r.mid AND m.seq = r.seq
WHERE r.uid = ".$logged_in_id."
AND r.status in ('A', 'N')
AND r.seq = (
SELECT
MAX(rr.seq)
FROM message_recipient rr
WHERE rr.mid = m.mid
AND rr.status in ('A', 'N')
)
AND IF (m.seq=1 and m.created_by = ".$logged_in_id." , 1=0, 1=1)
ORDER BY created_on DESC
LEFT JOIN users u
ON u.user_id = m.created_by
LEFT JOIN
位置错误。 所有JOIN都需要在WHERE
子句之前:
SELECT
m.mid,
m.seq,
m.created_on,
m.created_by,
m.body,
r.status,
u.username_clean
FROM message_recipient r
INNER JOIN message m
ON m.mid = r.mid AND m.seq = r.seq
LEFT JOIN users u
ON u.user_id = m.created_by
WHERE r.uid = ".$logged_in_id."
AND r.status in ('A', 'N')
AND r.seq = (
SELECT
MAX(rr.seq)
FROM message_recipient rr
WHERE rr.mid = m.mid
AND rr.status in ('A', 'N')
)
AND IF (m.seq=1 and m.created_by = ".$logged_in_id." , 1=0, 1=1)
ORDER BY created_on DESC
SQL子句按以下顺序排列:
SELECT
FROM
JOIN
WHERE
GROUP BY
ORDER BY
即使你有多个连接,它们也会出现在WHERE
之前
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