sql-server - 一个额外的内连接导致逻辑读取数量激增

Question

我有两张看起来几乎相同的 table 。当我选择其中任何一个时，我的逻辑读取次数约为 8.000-10.000 次读取。但是当我内部加入它们时，我得到了大约 380.000 次逻辑读取。

我使用 MS SQL 2012。

我遇到问题的查询如下所示:

SELECT ac.ID AS AccountID
    ,ab.Balance
    ,abc.BalanceInAccountCurrency
FROM dbo.Dates d
INNER JOIN dbo.Accounts ac ON d.[Date] BETWEEN ac.CreationDate AND ac.ClosureDate
INNER JOIN dbo.AccountBalances ab ON ab.AccountID  = ac.ID AND d.[Date] BETWEEN ab.CreationDate  AND ab.ClosureDate
INNER JOIN dbo.AccountBalancesInAccountCurrency abc ON abc.AccountID = ac.ID AND d.[Date] BETWEEN abc.CreationDate AND abc.ClosureDate
WHERE d.[Date] = DATEFROMPARTS(2017,06,20);

当我只像这样加入 AccountBalances 时:

SELECT ac.ID AS AccountID
      ,ab.Balance
FROM dbo.Dates d
INNER JOIN dbo.Accounts ac ON d.[Date] BETWEEN ac.CreationDate AND ac.ClosureDate
INNER JOIN dbo.AccountBalances ab ON ab.AccountID  = ac.ID AND d.[Date] BETWEEN ab.CreationDate  AND ab.ClosureDate
WHERE d.[Date] = DATEFROMPARTS(2017,06,20);

当我仅加入 AccountBalancesInAccountCurrency 时，我会得到类似的结果。

我的主键/聚集索引在两个表上都是这样的:

ALTER TABLE [dbo].[AccountBalances] ADD  CONSTRAINT [PK_AccountBalances] PRIMARY KEY CLUSTERED 
(
    ClosureDate DESC,
    CreationDate DESC,
    AccountID ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

我做错了什么？

执行计划

Both Tables

AccountBalancesInAccountCurrency Only

AccountBalances Only

额外信息

查询结果为 170460 行，总逻辑读取次数为 376.000。但如果我在查询中使用“top 170000”，则总逻辑读取次数仅为 44.000。统计 IO 如下所示:

And the execution plan looks like this

Answer 1

我找到了解决问题的方法。

1.AccountBalances 包含以银行记帐货币(丹麦克朗)表示的余额，AccountBalancesInAccountCurrency 包含以账户货币和丹麦克朗表示的余额。大多数货币为丹麦克朗，并且存在于两个表中。因此，我从 AccountBalancesInAccountCurrency 中删除了所有 DKK 余额，并对该表进行了左连接。

2.我还更改了 AccountBalancesInAccountCurrency 上的主键:

ALTER TABLE [dbo].[AccountBalances] ADD  CONSTRAINT [PK_AccountBalances] 
PRIMARY KEY CLUSTERED 
(
    ClosureDate DESC,
    CreationDate DESC,
    AccountID ASC
)

至:

ALTER TABLE [dbo].[AccountBalancesInAccountCurrency] ADD  CONSTRAINT 
[PK_AccountBalancesInAccountCurrency] PRIMARY KEY CLUSTERED 
(
    [AccountID] ASC,
    [ClosureDate] DESC
)

现在我的 IO 看起来像这样:

and my execution plan like this .

感谢所有引导我前进的评论。

节日快乐!