How can you use COUNT() in a comparison in a SELECT CASE clause in Sql Server?

Question

Let's say you want do something along the following lines:

SELECT CASE 
    WHEN (SELECT COUNT(id) FROM table WHERE column2 = 4) > 0
    THEN 1 ELSE 0 END

Basically just return 1 when there's one or more rows in the table, 0 otherwise. There has to be a grammatically correct way to do this. What might it be? Thanks!

Answer 1

You could do this:

SELECT CASE WHEN COUNT(ID) >=1 THEN 1 WHEN COUNT (ID) <1 THEN 0 END FROM table WHERE Column2=4

Reference: http://msdn.microsoft.com/en-us/library/ms181765.aspx

Answer 2

Question: return 1 when there's one or more rows in the table, 0 otherwise:

In this case, there is no need for COUNT. Instead, use EXISTS, which rather than counting all records will return as soon as any is found, which performs much better:

SELECT CASE 
    WHEN EXISTS (SELECT 1 FROM table WHERE column2 = 4)    
        THEN 1  
    ELSE 0 
END

Answer 3

Mahmoud Gammal posted an answer with an interesting approach. Unfortunately the answer was deleted due to the fact that it returned the count of records instead of just 1. This can be fixed using the sign function, leading to this more compact solution:

SELECT sign(count(*)) FROM table WHERE column2 = 4

I posted this because I find it and interesting approach. In production I'd usually end up with something close to RedFilter's answer.