TSQL where case

Question

I need the correct tsql syntax for this problem :

Select * from table where var_A='10'
select * from table where var_B='10'

When to use var_A or var_B depends on the value of var_C

So when var_c='something' use var_A='10' else var_B='10'

Solution 1

select *
from [table]
where case when var_c = 'something' then var_a else var_b end = '10'

SQL Fiddle with demo.

Solution 2

Ian probably has the best answer available but I thought I would supply another answer for a different (although less flexible) method in case it helps:

IF var_c = 'something' BEGIN
    SELECT * FROM [table] WHERE var_a = '10'
END
ELSE BEGIN
    SELECT * FROM [table] WHERE var_b = '10'
END