Question

By searching a number of SO threads I am unable to write a query which returns the appropriate condition in the where clause.
For example I have column Col1 which is int and a variable var1 as varchar now I used below query but it is not working.

Where CASE WHEN var1 = '1' THEN (Col1 = 1)  
WHEN var1 = '2' THEN (Col1 = 2)  
ELSE AND (1= 1) 
END

It gives me syntax error near '='.

EDIT:

What If I want condition like

Col1 IN (condtions….)

Answer 1

I think it should be like;

Where Col1 = CASE WHEN var1 IN ('1','2') THEN var1 ELSE Col1 END

OR

Where Col1 = CASE  var1 WHEN  '1' THEN 1
                        WHEN  '2' THEN 2
             ELSE Col1 END ...

As a side note, if Col1 is nullable and need to select those as well then use;

Where Col1 is null OR 
             Col1 = CASE  var1 WHEN  '1' THEN 1
                        WHEN  '2' THEN 2
             ELSE Col1 END ...