mysql查询运行缓慢

Question

我有这个问题

SELECT debtDinar,
       creditDinar,
       debtDollar,
       creditDollar AS creditDollar,
       companyID,
       costCenter,
       accountnumber,
       accountName,
       activityNo,
       activityName,
       name,
       if((debtDinar-creditDinar) >= 0.000,(debtDinar-creditDinar),0.000) AS debtDinarEx,
       if((debtDinar-creditDinar) >= 0.000,0.000,abs(debtDinar-creditDinar)) AS creditDinarEx,
       if((debtDollar-creditDollar) >= 0.00,(debtDollar-creditDollar),0.00) AS debtDollarEx,
       if((debtDollar-creditDollar) >= 0.00,0.00,abs(debtDollar-creditDollar)) AS creditDollarEx
FROM
  (SELECT SUM(recordsdetails.debtor) AS debtDinar,
          SUM(recordsdetails.creditor) AS creditDinar,
          SUM(recordsdetails.debtDollar) AS debtorDollar,
          SUM(recordsdetails.creditDollar) AS creditDollar,
          companies.name AS name,
          recordsdetails.companyID AS companyID,
          costCenter AS costCenter,
          accounts.accountnumber AS accountnumber,
          accounts.accountName AS accountName,
          recordsdetails.activityNo AS activityNo,
          recordsdetails.activityName AS activityName
   FROM (records,
         accounts
         JOIN (companies
               LEFT JOIN recordsdetails on((recordsdetails.companyID = companies.companyID))))
   WHERE left(recordsdetails.accountnumber,1)=accounts.accountnumber
     AND (recordsdetails.companyID = 1)
   GROUP BY accounts.accountnumber,
            costCenter
   ORDER BY accounts.sortorder) AS recordsdetails   

获取数据的速度非常慢，大约需要 30-60 秒，当数据增加时它会变得更慢，有什么想法可以让这个查询变得简单

Answer 1

我先整理一下您的查询。您使用了混合连接语法，缺少别名并将临时表重命名为与真实表相同的名称，因此很难跟踪正在发生的事情。

你真的在使用表records吗？它似乎是在没有任何条件的情况下交叉加入的..

您也可以重构 SELECT FROM (SELECT ... )。

一旦这一切都干净整洁，您应该运行EXPLAIN ... 并查看正在使用哪些索引以及查询可能在哪里失败。