mysql - 如何优化包含连接和子查询的 sql 联合

Question

我查看了很多有关sql优化的评论，但找不到答案。

我的应用程序使用此 SQL ...

SELECT * FROM ((
  SELECT DISTINCT 
      c.companyname,
      c.tradingas,
      a.quarantined,
      c.companyid,
      a.address1,
      a.city,
      a.postcode,
      a.region,
      c.origin_dsn,
      d.title,
      d.firstname,
      d.surname,
      d.position,
      a.telephoneno,
      a.companyemail,
      addresstypes,
      markets 
    FROM companies c
    join addresses a on c.companyid = a.companyid
    join contacts d on c.companyid = d.companyid
    where d.origin_dsn = 'ifd'
      and primarycontact = 1
      and d.clientid = 0
      and c.origin_dsn = 'ifd' and
      a.origin_dsn = 'ifd' and
      c.companyid in (
        select distinct companyid
        from products
        where description IN ('Windows and Doors','Vertical Sliders','Bi-Fold Doors')
          AND type IN ('wd:f','wd:b')
          AND material = 'PVCu'
          AND origin_dsn = 'ifd'
  ))
  UNION (
    SELECT DISTINCT
      c.companyname,
      c.tradingas,
      a.quarantined,
      c.companyid,
      a.address1,
      a.city,
      a.postcode,
      a.region,
      c.origin_dsn,
      d.title,
      d.firstname,
      d.surname,
      d.position,
      a.telephoneno,
      a.companyemail,
      addresstypes,
      markets
    FROM companies c
    join addresses a on c.companyid = a.companyid
    join contacts d on c.companyid = d.companyid
    where d.origin_dsn = 'ifd'
      and primarycontact = 1
      and d.clientid = 0
      and c.origin_dsn = 'ifd'
      and a.origin_dsn = 'ifd'
      and c.companyid in (
        select distinct companyid
        from products
        where type IN ('cr:f','cr:b')
          AND origin_dsn = 'ifd')
      )
  ) as t
  where t.quarantined = 0
    and t.origin_dsn = 'ifd'
    and t.region IN (
      'Northern Counties','North West','Yorkshire',
      'East Midlands','West Midlands','South West',
      'Home Counties','Southern Counties','Greater London',
      'Scotland','Wales','Northern Ireland')
  order by companyname

在 mysql 查询浏览器中运行需要惊人的 3.5 秒(在我的慢速、低规范笔记本电脑上)

此查询由 2 个非常相似的查询组成，每个查询大约需要 1.5 秒。

我的应用程序可能需要最多 4 个类似的联合。

谁能建议如何更有效地编写它？

Answer 1

我会将贵公司的产品标准首先移至预查询... 然后加入以获取其他详细信息...因此您的公司 ID 只会预先选择一次。预查询，您可以按照我在此处采样的方式加入多个条件...

where 
      ( first set of criteria )
   OR ( second set of criteria )
   OR ( third set of criteria )

(但是，您的两个条件都使用 origin_dsn = 'ifd' ，这可能会被简化一次，但我不知道您的条件实际上是如何构造的)。

为了帮助优化查询，在您的产品表上，我会确保 (Origin_DSN，type，material)的索引

对于地址表，索引为(companyid、origin_dsn、quaranted、region)

对于联系人表，索引为(companyid、origin_dsn、clientid)

类似...

SELECT DISTINCT 
      c.companyname,
      c.tradingas,
      a.quarantined,
      c.companyid,
      a.address1,
      a.city,
      a.postcode,
      a.region,
      c.origin_dsn,
      d.title,
      d.firstname,
      d.surname,
      d.position,
      a.telephoneno,
      a.companyemail,
      addresstypes,
      markets 
   FROM 
      ( select distinct 
              p.companyid
           from 
              products p
           where 
                 (     p.origin_dsn = 'ifd' 
                   AND p.`type` IN ('cr:f','cr:b') )
              OR (     p.origin_dsn = 'ifd' 
                   AND p.`type` IN ('wd:f','wd:b')
                   AND p.material = 'PVCu' 
                   AND p.description IN ('Windows and Doors','Vertical Sliders','Bi-Fold Doors') ) ) as PreQuery

         JOIN companies c
            ON PreQuery.CompanyID = c.CompanyID


            join addresses a 
               on c.companyid = a.companyid
              and c.origin_dsn = a.origin_dsn 
              and a.quarantined = 0
              and a.Region in ( 'Northern Counties',
                                'North West',
                                'Yorkshire',
                                'East Midlands',
                                'West Midlands',
                                'South West',
                                'Home Counties',
                                'Southern Counties',
                                'Greater London',
                                'Scotland',
                                'Wales',
                                'Northern Ireland' )
            join contacts d 
               on c.companyid = d.companyid
              AND c.origin_dsn = d.origin_dsn 
              and d.clientid = 0
   where 
          primarycontact = 1
      and c.origin_dsn = 'ifd' 
   order by 
      c.companyname