SQL conditional SELECT

Question

I would like to create a stored procedure with parameters that indicate which fields should be selected.

E.g. I would like to pass two parameters "selectField1" and "selectField2" each as bools.

Then I want something like

SELECT  if (selectField1 = true) Field1 ELSE do not select Field1  if (selectField2 = true) Field2 ELSE  do not select Field2  FROM Table 

Thanks Karl

Answer 1

In SQL, you do it this way:

SELECT  CASE WHEN @selectField1 = 1 THEN Field1 ELSE NULL END,         CASE WHEN @selectField2 = 1 THEN Field2 ELSE NULL END FROM    Table 

Relational model does not imply dynamic field count.

Instead, if you are not interested in a field value, you just select a NULL instead and parse it on the client.

Answer 2

You want the CASE statement:

SELECT   CASE      WHEN @SelectField1 = 1 THEN Field1     WHEN @SelectField2 = 1 THEN Field2     ELSE NULL   END AS NewField FROM Table 

EDIT: My example is for combining the two fields into one field, depending on the parameters supplied. It is a one-or-neither solution (not both). If you want the possibility of having both fields in the output, use Quassnoi's solution.