使用SUM()的MySQL查询缓慢

我必须在代码中运行两个查询才能使我的租户保持平衡.但是,这些查询太慢了.

首先查询,我得到了所有租户,它是单位名称：

SELECT t.TenantID 
  FROM Tenants t
  JOIN Units u
    ON t.UnitID = u.UnitID
 Where t.Prospect = 2 
   AND t.PropertyID = 8
 ORDER 
    BY CONCAT(Left(Replace(UnitName,'-',''),2),
              REPEAT('0', (10-CHAR_LENGTH(UnitName))),
              Right(Replace(UnitName,'-',''),
                    CHAR_LENGTH(Replace(UnitName,'-',''))-2
             )     )

返回500行

然后我得到4种条件下的余额.该查询将在第一个查询循环中：

Select
        SUM(CASE WHEN TransactionTypeID = 1 AND ChargeTypeID != 6 THEN TransactionAmount ELSE 0 END) AS TotalDebit,
        SUM(CASE WHEN TransactionTypeID = 1 AND ChargeTypeID = 6 THEN TransactionAmount ELSE 0 END) AS HousingDebit,
        SUM(CASE WHEN TransactionTypeID = 2 AND ChargeTypeID != 6 THEN TransactionAmount ELSE 0 END) AS TotalCredit,
        SUM(CASE WHEN TransactionTypeID = 2 AND ChargeTypeID = 6 THEN TransactionAmount ELSE 0 END) AS HousingCredit
    From TenantTransactions
    Where TenantID= FirstQuery.TenantID

我做错查询了吗？运行大约需要1分钟.

解决方法:

使用GROUP BY在单个查询中执行此操作.

尝试这样的事情：

SELECT t.TenantID, TotalDebit, HousingDebit, TotalCredit, HousingCredit
  FROM Tenants t
  JOIN Units u ON t.UnitID = u.UnitID
  LEFT JOIN (
        Select
          TenantID,
          SUM(CASE WHEN TransactionTypeID = 1 AND ChargeTypeID != 6 THEN TransactionAmount ELSE 0 END) AS TotalDebit,
          SUM(CASE WHEN TransactionTypeID = 1 AND ChargeTypeID = 6 THEN TransactionAmount ELSE 0 END) AS HousingDebit,
          SUM(CASE WHEN TransactionTypeID = 2 AND ChargeTypeID != 6 THEN TransactionAmount ELSE 0 END) AS TotalCredit,
          SUM(CASE WHEN TransactionTypeID = 2 AND ChargeTypeID = 6 THEN TransactionAmount ELSE 0 END) AS HousingCredit
        From TenantTransactions
       Group By TenantID
       ) sums ON sums.TenantID = t.TenantID
 Where t.Prospect = 2 
   AND t.PropertyID = 8
 ORDER 
    BY CONCAT(Left(Replace(UnitName,'-',''),2),REPEAT('0', (10-CHAR_LENGTH(UnitName))),Right(Replace(UnitName,'-',''),CHAR_LENGTH(Replace(UnitName,'-',''))-2))

内部查询可能仍会运行一段时间,但只会运行一次.

尝试对包含以下列的TenantTransactions进行覆盖的复合索引：(TenantID,TransactionTypeID,ChargeTypeID,TransactionAmount),以优化其中包含SUM的查询.

在其中包含列(PropertyID,Prospect)的租户上尝试复合索引.

标签：query-performance,mysql
来源： https://codeday.me/bug/20191110/2013868.html