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TOP_MySQL

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Release: 2016-05-30 17:09:47
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TOP 关键字结合SELECT 查询使用,显示前几条的记录

 

常有两种使用方式:

 

一、选择前N条记录

 

示例1:查询出病假时间较少的前10个职员的信息

 

1 USE AdventureWorks2014

2 SELECT TOP 10 [SickLeaveHours]

3 FROM [HumanResources].[Employee]

4 ORDER BY [SickLeaveHours] 

查询结果:

 

  SickLeaveHours

 

 

 1 20

 2 20

 3 20

 4 20

 5 20

 6 20

 7 21

 8 21

 9 21

10 21

 

 

 

二、选择前N%的记录

 

示例2:查询病假时间较少的前百分之2个职员的信息

 

1 USE AdventureWorks2014

2 SELECT TOP 2 PERCENT [SickLeaveHours]

3 FROM [HumanResources].[Employee]

4 ORDER BY [SickLeaveHours]

查询结果:

 

  SickLeaveHours

 

1 20

2 20

3 20

4 20

5 20

6 20

 

 

特别的,WITH TIES 关键字的使用:

 

一般包含TOP的查询显示规定数量的结果,TOP N 只显示N条记录,对于TOP N PERCENT 只显示总数N%的结果。

 

但是包含WITH TIES 的查询在先显示规定数量的结果后,与结果最后一条记录的排序字段值相同的记录也被显示

 

示例3:在实例1的基础上加上WITH TIES 关键字

 

1 USE AdventureWorks2014

2 SELECT TOP 10 WITH TIES [SickLeaveHours]

3 FROM [HumanResources].[Employee]

4 ORDER BY [SickLeaveHours]

查询结果:

 

   SickLeaveHours

 

 

 1 20

 2 20

 3 20

 4 20

 5 20

 6 20

 7 21

 8 21

 9 21

10 21

11 21

12 21

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