SQL query returning values based on values in the same row

Question

Is there a way to write a query that returns a value from a different row in the same table based on a value in a row and have it return that value on the same row?

I have a table with columns SC_CODE , SC_DESC , SC_ALT_CODE , and SC_CANX_CODE :

• SC_CODE values are 1 , 2 , 901 , 902 , etc.
• SC_DESC values are Test1 , Test2 , Test3 , Test4 , etc.
• SC_ALT_CODE values are NULL , 3 , 4 , NULL , etc.
• SC_CANX_CODE values are 901 , 902 , 903 , 904 , etc.

My query needs to return something like:

1, Test1, NULL, 901, Test3
2, Test2, 3, 902, Test4

Here, Test3 is the SC_DESC of SC_CODE 901 and Test4 is the SC_DESC of SC_CODE 902 , etc.

Answer 1

I think this should work for you:

DECLARE @TEST AS TABLE
(
        SC_CODE INT
    ,   SC_DESC VARCHAR(255)
    ,   SC_ALT_CODE INT
    ,   SC_CANX_CODE INT 
)

INSERT @TEST (SC_CODE, SC_DESC, SC_ALT_CODE, SC_CANX_CODE)
VALUES (1, 'Test1', NULL, 901)
,       (2, 'Test2', 3, 902)
,       (901, 'Test3', 4, 903)
,       (902, 'Test4', NULL, 904)
,       (3, 'Test5', NULL, NULL)

SELECT  T.SC_CODE
,       T.SC_DESC
,       T.SC_ALT_CODE
,       T.SC_CANX_CODE
,       T2.SC_DESC AS CANX_DESC
,       T3.SC_DESC AS ALT_DESC
FROM    @TEST AS T
JOIN    @TEST AS T2
    ON  T2.SC_CODE = T.SC_CANX_CODE
LEFT JOIN   @TEST AS T3
    ON  T3.SC_CODE = T.SC_ALT_CODE

Result:

+---------+---------+-------------+--------------+-----------+----------+
| SC_CODE | SC_DESC | SC_ALT_CODE | SC_CANX_CODE | CANX_DESC | ALT_DESC |
+---------+---------+-------------+--------------+-----------+----------+
|       1 | Test1   | NULL        |          901 | Test3     | NULL     |
|       2 | Test2   | 3           |          902 | Test4     | Test5    |
+---------+---------+-------------+--------------+-----------+----------+

Edit Added a join for SC_ALT_CODE as asked in comment. Note I added a row to the sample data to get result. Also note the use of LEFT JOIN , not every record has an Alternative. With LEFT JOIN you don't loose those records.

Answer 2

Its still not entirely clear what you are trying to do but I think you are looking for the LEAD function with an offset of 2, to produce the desired result:

CREATE TABLE #tbltmp(
SC_CODE int,
SC_DESC varchar(5),
SC_ALT_CODE int,
SC_CANX_CODE int);

INSERT INTO #tbltmp values 
(1,'Test1',NULL,901),
(2,'Test2',3,902),
(901,'Test3',4,903),
(902,'Test4',NULL,904);

SELECT
SC_CODE,
SC_DESC,
SC_ALT_CODE,
SC_CANX_CODE,
LEAD(SC_DESC,2) OVER (ORDER BY SC_DESC) SC_DESC
FROM #tbltmp

DROP TABLE #tbltmp