How to select top N salaries for each person?

Question

I have the table

user_id  salary month
1        100    1
1        150    2
1        200    3
1        180    4
1        140    5
2        10     1
2        40     2
2        20     3
2        15     4
2        45     5

I want to select top 2 salaries for each people.

I try to understand cross apply. looks like my invented task conform the cross apply.

Now I have the following query

select distinct(s.user_id) from Salary s
cross apply (
     select top 2 * from Salary  sal
     order by sal.salary desc
)sal

look like I enough far from expected result.

expected result:

1    180
1    200
2    40
2    45

Answer 1

You can use OUTER APPLY with TOP 2:

SELECT DISTINCT 
            y.[user_id],
            d.salary,
            d.[month]
FROM YourTable y
OUTER APPLY(
    SELECT TOP 2  *
    FROM YourTable
    WHERE y.[user_id] = [user_id]
    ORDER BY [user_id], salary DESC
    ) as d
ORDER BY [user_id], salary DESC

Will return:

user_id salary  month
1       200     3
1       180     4
2       45      5
2       40      2

Another way:

;WITH cte AS (
SELECT  *,
        ROW_NUMBER() OVER (PARTITION BY [user_id] ORDER BY salary DESC) as rn
FROM YourTable
)

SELECT [user_id], salary, [month]
FROM cte 
WHERE rn <= 2

Same output.