记录一次PageHelper插件和SQL不规范导致的慢查询问题
一 问题描述
通过查看慢查询语句,发现类似如下的慢查询语句,t_a表数据量大概50多万,查询耗时大概是3秒。
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SELECT COUNT(0)
FROM (
SELECT a.id, a.bbbb, b.cccc, c.aaaa1, d.bbbbb2, d.ccccc3
FROM t_a a
LEFT JOIN t_b b ON a.aa_id = b.id
LEFT JOIN t_c c ON b.bb_id = c.id
LEFT JOIN t_d d ON c.cc_id = d.id
WHERE 1 = 1
AND
...more >>