Question

I have a table INFO whose design is like this

id - bigint
Name - varchar2
refid - bigint
status - int
ExpDate - datetime

• status values can be 0,1,2,3,4
• refid is the foreign key of other table which we are going to use too

I want to write a query where all records should come from this table with status 0, 1, 2, 3, but only 7 latest records by expdate should come whose status is 4.

I can’t figure out how can we achieve this in T-SQL.

Please help me out or give me suggestion so that I can start writing it.

Upto now I have written

SELECT * 
FROM INFO 
WHERE STATUS IN (0,1,2,3) AND 
      REFID IN (SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW')

SELECT TOP 7
FROM INFO 
WHERE STATUS=4 AND 
      REFID IN(SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW') 
ORDER BY EXPDATE DESC

i need to join them??? how.. suggest and also the query

(SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW') 

is coming twice how to optimize it thanks..

Answer 1

Just UNION your 2 current queries together (you need a derived table to get the TOP though)

SELECT ...
FROM INFO 
WHERE STATUS IN (0,1,2,3) AND 
      REFID IN (SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW')
UNION ALL
SELECT ...
FROM 
    (
    SELECT TOP 7 ...
    FROM INFO 
    WHERE STATUS=4 AND 
          REFID IN(SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW') 
    ORDER BY EXPDATE DESC
    ) T

You can get fancier, but it may not be as efficient:

SELECT *
FROM
    (
    SELECT ...,
       ROW_NUMBER() OVER (ORDER BY EXPDATE DESC) AS rn
    FROM INFO 
    WHERE REFID IN (SELECT REFID FROM REFTABLE WHERE REFCHAIN='BMW')
    ) T
WHERE
    rn <= 7 OR STATUS <= 4