[英]Query executes very slow?
我有一个表,其中有四列 ID、MID、SID 和 Amt,我准备查询以使用 level 计算 amt 的总和。
喜欢:
SELECT Sum(amt) as level1 FROM adm where sid='MT00001';
SELECT Sum(amt) as level2 FROM adm where sid in (SELECT mid FROM adm where sid='MT00001');
SELECT Sum(amt) as level3 FROM adm where sid in (SELECT mid FROM adm where sid in (SELECT mid FROM adm where sid='MT00001'));
SELECT Sum(amt) as level4 FROM adm where sid in (SELECT mid FROM adm where sid in (SELECT mid FROM adm where sid in (SELECT mid FROM adm where sid='MT00001')))
但是花了很多时间,我想要这个直到第 15 级
EXPLAIN [your query here]
这将帮助您了解查询和表的当前状态。
在表上添加索引将有助于提高查询性能。
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