sql - 需要一些关于优化此查询的想法

Question

我有下面的查询，我正在寻找优化它的方法（等使其更高效和更快）。有没有人有任何想法？

SELECT s.oem_id, s.name, SUM(u.minimum_gfs) AS minimum_gfs, sum(u.minimum_ofs) AS    
   minimum_ofs, sum(u.minimum_wq) AS minimum_wq
FROM nmp_building_reqs AS s
   LEFT OUTER JOIN nmp_building_util AS u
ON u.oem_id = s.oem_id
GROUP BY s.oem_id, s.name

Answer 1

唯一明显的事情是确保 oem_id 被索引以使连接更快。

但是，我怀疑您可以在加入之前进行聚合，然后引入名称。这是假设 oem_id 只有一个与之关联的名称。查询如下所示：

SELECT s.oem_id, s.name, u.minimum_gfs, u.minimum_ofs, u.minimum_wq
FROM nmp_building_reqs s left outer join
     (select u.oem_id, SUM(u.minimum_gfs) AS minimum_gfs,
             sum(u.minimum_ofs) AS minimum_ofs, sum(u.minimum_wq) AS minimum_wq
      from nmp_building_util u
      group by u.oem_id
     ) u
     ON u.oem_id = s.oem_id