Question

我正在执行以下查询。只有17个记录需要80秒。

任何人都可以告诉我理由是否知道。我已经尝试过索引。

SELECT DISTINCT t.i_UserID,
                u.vch_LoginName,
                t.vch_PreviousEmailAddress AS 'vch_EmailAddress',
                u.vch_DisplayName,
                t.d_TransactionDate AS 'd_DateAdded',
                'Old' AS 'vch_RecordStatus'
           FROM tblEmailTransaction t
     INNER JOIN tblUser u 
             ON t.i_UserID = u.i_UserID
          WHERE t.vch_PreviousEmailAddress LIKE '%kala%'

Answer 1

更改vch_PreviousEmailAddress

上Latin1_General_100_BIN2列的排序规则

创建覆盖索引：

CREATE NONCLUSTERED INDEX ix
ON dbo.tblEmailTransaction (vch_PreviousEmailAddress)
    INCLUDE (i_UserID, d_TransactionDate)
GO

欢迎使用此查询：

SELECT t.i_UserID,
       u.vch_LoginName,
       t.vch_PreviousEmailAddress AS vch_EmailAddress,
       u.vch_DisplayName,
       t.d_TransactionDate AS d_DateAdded,
       'Old' AS vch_RecordStatus
FROM (
    SELECT DISTINCT i_UserID,
                    vch_PreviousEmailAddress,
                    d_TransactionDate
    FROM dbo.tblEmailTransaction
    WHERE vch_PreviousEmailAddress LIKE '%kala%' COLLATE Latin1_General_100_BIN2
) t
JOIN dbo.tblUser u ON t.i_UserID = u.i_UserID

Answer 2

另一件事，我觉得在解决这样的问题时很有用：

尝试运行以下脚本。它会告诉您可以向SQL Server数据库询问哪些索引，哪些索引会得到最大的改善。

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
SELECT TOP 100 
  ROUND(s.avg_total_user_cost * s.avg_user_impact * (s.user_seeks + s.user_scans),0) AS 'Total Cost',
  s.avg_user_impact,
  d.statement AS 'Table name',
  d.equality_columns, 
  d.inequality_columns,
  d.included_columns,
  'CREATE INDEX [IndexName] ON ' + d.statement + ' ( ' 
     + case when (d.equality_columns IS NULL OR d.inequality_columns IS NULL)
       then ISNULL(d.equality_columns, '') + ISNULL(d.inequality_columns, '')
       else ISNULL(d.equality_columns, '') + ', ' + ISNULL(d.inequality_columns, '')
     end + ' ) '
     + CASE WHEN d.included_columns IS NULL THEN '' ELSE 'INCLUDE ( ' + d.included_columns + ' )' end AS 'CREATE INDEX command'
FROM sys.dm_db_missing_index_groups g,
     sys.dm_db_missing_index_group_stats s, 
     sys.dm_db_missing_index_details d 
WHERE d.database_id = DB_ID() 
AND s.group_handle = g.index_group_handle 
AND d.index_handle = g.index_handle
ORDER BY [Total Cost] DESC

右侧列显示您需要运行的CREATE INDEX命令，以创建该索引。

这个救生员脚本中的一个，我经常在我们的内部数据库上运行。

但是，在您的示例中，这可能会告诉您需要vch_PreviousEmailAddress表中tblEmailTransaction字段的索引。

Answer 3

可能的瓶颈是2：

在tblEmailTransaction.i_UserID上缺少索引：检查表是否具有索引
缺少tblUser.i_UserID上的索引：检查表是否具有索引
Like Statement：正如Devart所建议的那样，语句被认为性能不佳，尝试以这种方式指定集合：
```
 WHERE vch_PreviousEmailAddress LIKE '%kala%' COLLATE Latin1_General_100_BIN2
```

要更好地查看查询，必须使用查询运行此命令：

SET IO STATISTICS ON

它将写入查询所做的所有IO Access，我们可以看到发生了什么。

最后一个问题？这两个表包含多少行？

侨

sqlserver查询时间

3 个答案: