Question

I need to insert into new table (2 columns) Distinct description from other table and in second row case.

So like:

Insert into @Temp1
Select distinct description from Table1,
CASE
WHEN aaa then 1
When bbb then 2
END

So basically for every inserted value in first column, in second column goes one of several possible values, depending on first value.

Is this possible?

Answer 1

Yes this is possible. Looks like you are missing the input_expression from your Simple CASE expression and have the FROM in the wrong place..

INSERT INTO @Temp1
SELECT DISTINCT description,
                CASE description
                  WHEN aaa THEN 1
                  WHEN bbb THEN 2
                END
FROM   Table1

Of course if aaa etc are constants rather than derived from other columns in Table1 such that the second column can be deterministically derived from the first column (and it isn’t going to be altered in future updates) there might not be any point in storing it at all. You can define the table variable with a computed column definition or simply use the CASE expression when SELECT-ing from it.

Example of the computed column case

DECLARE @Temp1 TABLE (
  [description] VARCHAR(50),
  [calcColumnExample] AS CASE description
       WHEN 'aaa' THEN 1
       WHEN 'bbb' THEN 2
     END 
)