如何从sql查询中找到第n行？

Question

I have a table in which data is something like this:

Name    Salary
Tom      10000
John     20000
Ram      20000
Danny    15000
Sandy    14000
Riddle   15000

I can find 2nd highest salary using cte ;

with cte
as
(
    select ROW_NUMBER() over (order by Salary desc) as r,
    * from Employee e
)
select * from cte where r=2

But this gives the result 'Ram' with 20000 salary. What I would like returned is every record for people with the nth-ranking salary. For instance, if I'm looking for n=2 , the result would be:

Danny    15000
Riddle   15000

How do I modify the query to achieve this?

Answer 1

Use DENSE_RANK() :

;WITH cte AS
(
    SELECT DENSE_RANK() OVER (ORDER BY Salary DESC) AS r, *
    FROM Employee e
)
SELECT *
FROM cte
WHERE r = 2

SQL Fiddle

Answer 2

Try this query:

WITH
cte AS
(select DENSE_RANK() over (ORDER BY Salary desc) AS R, e.*
from Employee e)
SELECT * From cte
WHERE R =2

Here is a SQLFiddle

Answer 3

I posted about this on my blog: https://fullparam.wordpress.com/2015/03/31/sql-select-nth-rank-of-something-three-approaches/

Correlated subquery:

SELECT FirstName, LastName, BaseRate
FROM DimEmployee e
WHERE (SELECT COUNT(DISTINCT BaseRate)
    FROM DimEmployee p WHERE e.BaseRate=p.BaseRate) = 4

Why is this a good answer? It's not really but this will work on any SQL implementation. It's fairly slow, it will do a lot of look ups. The subquery is evaluated every time a row is processed by the outer query. This query uses dense ranking and can return multiple rows.

Double Order By with TOP statement:

SELECT TOP 1 FirstName, LastName, BaseRate
FROM ( SELECT TOP 4 FirstName, LastName, BaseRate
    FROM DimEmployee ORDER BY BaseRate DESC) AS MyTable
ORDER BY BaseRate ASC;

Why is this a good answer? Because it is an easy syntax to remember. Let's look at the subquery, which returns the N highest salaries in the DimEmployee table in descending order. Then, the outer query will re-order those values in ascending (default) order, this means the Nth highest salary will now be the topmost salary. Keep in mind that the TOP statement is MS SQL server specific. MySQL would use LIMIT 1 for instance. In addition this solution cannot do DENSE ranking and only returns one row even if two employees share the same BaseRate.

Use Windowing function:

SELECT FirstName, LastName, BaseRate
FROM (SELECT FirstName, LastName, BaseRate, DENSE_RANK() OVER (ORDER BY BaseRate DESC) Ranking
FROM DimEmployee) AS MyTable
WHERE Ranking = 4

Why is this a good answer? Because it performs the best – performance is king. The Syntax is also ANSI SQL however of the “Big 3” only Oracle and MS are using it. In addition you can chose to use ROW_NUMBER, DENSE_RANK or regular RANK.

Answer 4

The DISTINCT keyword might help you here.

SELECT Salary FROM Employee order by Salary desc

will return

20000
20000
15000
15000
14000
10000

but add DISTINCT

SELECT DISTINCT Salary FROM Employee order by Salary desc

will return

20000
15000
14000
10000

So which do you want, the third highest person by salary (which isn't guaranteed to always be the same, as two people might share the 15,000 salary), or the people who have the third highest salary (which in this case, is only one person who has the 14,000 salary, but that's no guarantee.

Answer 5

u can get the 2nd highest salary by using CO-RELATED Query as follows:

select name from employee e1   --outer query

   where 2= --2nd highest salary

(select COUNT(e2.salary)       --inner query

from employee e2 where e2.salary >= e1.salary)