您好我有一个查询,通过显示评价首先评论然后评论尚未评价的评论来做我想做的事情。但是我似乎无法正确订购。
结果如何:
5
4
0
0
...
目前正在这样做:
4
5
0
0
...
这是我的查询
$sql = $db->query( "
SELECT branch.*, MAX(review.rating) AS m
FROM branch
LEFT OUTER JOIN review ON branch.bid = review.bid
WHERE branch.address2 LIKE '$query' OR branch.postcode LIKE '$query-%'
GROUP BY branch.bid
ORDER BY m DESC, branch.branch ASC
LIMIT $start,$limit
" ) or die( "Select failed: (" . $db->errno . ") " . $db->error );
答案 0 :(得分:1)
Meghraj Choudhary的子查询解决方案应该有效。
但是,加入更快。子查询需要额外的磁盘访问。假设branch.bid
是主键,以下内容应该更快:
SELECT b1.*, b2.m FROM branch b1
INNER JOIN
(
SELECT branch.bid, MAX(review.rating) AS m
FROM branch
LEFT OUTER JOIN review ON branch.bid = review.bid
WHERE branch.address2 LIKE '$query' OR branch.postcode LIKE '$query-%'
GROUP BY branch.bid
LIMIT $start,$limit
) b2 ON
b1.bid = b2.bid
ORDER BY b2.m DESC, b1.branch ASC
我没试过这个。所以,请尝试并发回。