如何优化此查询？它检索列的值

Question

如何在MySQL中优化此查询？从该省取回市政府？ TIA

select DISTINCT PM.municipality, count(*)
from anReference as R
inner join anFieldInfo as F on R.ref_id = F.ref_id
inner join tblProvince as PP on F.province_id = PP.province_id
inner join tblMunicipality as PM on F.municipality_id = PM.municipality_id
WHERE R.category = 0 AND R.test = 1
AND PP.region_id=2
AND PM.province_id=7
AND R.date_accessed between '2016-11-01 00:00:00' and '2016-11-30 23:59:00'
GROUP BY PM.municipality;

这是我运行EXPLAIN时得到的结果。

Answer 1

如果你得到夸大的值，那么考虑重写类似的东西：

SELECT PM.municipality, count(*)
    FROM PM
    WHERE tblMunicipality AS PM.province_id=7
      AND EXISTS ( ... )
    GROUP BY PM.municipality

子查询（在EXISTS中）是所有其他表的JOINs。

暂且不说：这是测试一个月范围的“更简单”方式：

AND R.date_accessed >= '2016-11-01'
AND R.date_accessed  < '2016-11-01' + INTERVAL 1 MONTH