Question

我需要以最有效的方式获取薪水第三高的员工的所有细节。

我的查询：

select(SELECT MIN(Salary)
FROM   (SELECT * TOP (3) Salary
       FROM   Employees
       ORDER  BY Salary)

我的查询中是否有任何问题。我可以更正我的查询。请帮助。

Answer 1

使用RANK

; WITH T AS
(
   SELECT * , RANK() OVER (ORDER BY SalaryDESC) as rk
   FROM Employees 
)    
Select TOP(1) *
FROM T
WHERE T.rk=3

Answer 2

你可以使用 Rownumber ：这里我用empid分区以避免关系

;With cte
as
(
select *,row_number() over (partition by empid order by salary desc) as rownum
from 
table
)
select * from cte where rownum=3

如果您想使用您的查询：

SELECT MIN(Salary
FROM   (
SELECT  TOP (3) Salary
       FROM   Employees
       ORDER  BY Salary
)b

Answer 3

有几种方法可以做到这一点。

有两种可能的方法

使用row_number（或其他窗口函数，例如rank或dense_rank）
在子查询上使用top，然后在结果集上使用

我建议不使用row_number，因为这需要更多的cpu，而是使用上述两种方法中的后者。

以下是两者的测试用例，显示的是子查询方法在不到四分之一的时间内运行。

create table #Salary (
    PersonId int identity(1, 1) primary key clustered,
    SalaryAmt decimal(16, 2) not null);

/* Insert some test data ... */
insert #Salary (
    SalaryAmt)
select top (10000000)
    abs(checksum(newid()) % 1000000)
from sys.all_columns a
cross join sys.all_columns b

set statistics io on;
set statistics time on;

select *
from (
    select *,
        RowNum = row_number() over (order by SalaryAmt desc)
    from #Salary) a
where RowNum = 3;

set statistics time off;
set statistics io off;

checkpoint;
go
dbcc dropcleanbuffers;
go

set statistics io on;
set statistics time on;

select top 1 *
from (
    select top 3 *
    from #Salary
    order by SalaryAmt desc) top_3
order by SalaryAmt;

set statistics time off;
set statistics io off;

结果如下：

SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 1 ms.
PersonId    SalaryAmt                               RowNum
----------- --------------------------------------- --------------------
1427822     999999.00                               3

Table '#Salary_____________________________________________________________________________________________________________000000000007'. Scan count 9, logical reads 27219, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.


 SQL Server Execution Times:
   CPU time = 17123 ms,  elapsed time = 2361 ms.
DBCC execution completed. If DBCC printed error messages, contact your system administrator.
SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.
PersonId    SalaryAmt
----------- ---------------------------------------
1427822     999999.00

Table '#Salary_____________________________________________________________________________________________________________000000000007'. Scan count 9, logical reads 27219, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.


 SQL Server Execution Times:
   CPU time = 4282 ms,  elapsed time = 570 ms.

希望这有帮助。

获得薪水第三高的员工

3 个答案: