Question

I got a table like this

AMID     Entry
------- ---------
1000     MARS
1001     JUPITER
1002     SATURN
1003     VENUS
1003     SATURN
1004     NEPTUNE
1004     SATURN
1005     JUPITER
1005     MARS

Now I want to extract the DISTINCT AMID values with particular ENTRY values.
The end table should be like this

 AMID     Entry
-------- --------
  1000    MARS
  1001    JUPITER
  1002    SATURN
  1003    VENUS
  1004    SATURN
  1005    MARS

The condition to select ENTRY values is,

It has to take the values based on this priority :

1. VENUS
2. MARS
3. JUPITER
4. SATURN
5. NEPTUNE

So If any AMID has both VENUS and MARS, it should take VENUS
MARS and SATURN, it should take MARS
NEPTUNE and JUPITER, it should take JUPITER.(select by priority).

Answer 1

You can do it with ranking functions (if you’re using SQL Server 2008):

DECLARE @t TABLE (AMID INT, Entry VARCHAR(100))
INSERT @t 
VALUES
(       1000                   ,'MARS'),
(       1001                   ,'JUPITER'),
(       1002                   ,'SATURN'),
(       1003                   ,'VENUS'),
(       1003                   ,'SATURN'),
(       1004                   ,'NEPTUNE'),
(       1004                   ,'SATURN'),
(       1005                   ,'JUPITER'),
(       1005                   ,'MARS')

;WITH a AS(
    SELECT  *,
            ROW_NUMBER() OVER (PARTITION BY AMID ORDER BY 
                CASE Entry 
                    WHEN 'VENUS' THEN 0
                    WHEN 'MARS' THEN 1
                    WHEN 'JUPITER' THEN 2
                    WHEN 'SATURN' THEN 3
                    WHEN 'NEPTUNE' THEN 4
                END) num
    FROM    @t
)

SELECT  AMID, Entry
FROM    a
WHERE   num = 1