使用嵌套的案例表达

Question

I am stuck in properly using Nested Case Expression.

The requirement is to create the calculated column that will be either 0 or 1. If the name is 'abc' and ind = 1, then the value of calc column will be 1 . But if the name is 'abc' and salary is > 2000 . then the value will be 1 again irrespective the value of ind.

I have written the below query using OR condition in CASE Expression but want to use the Nested CASE.

select t.*,  case when (name = 'abc' and ind = 1 ) or (name = 'abc' and sal > 2000) 
                  then 1 
                  else 0 
                  end 
from test t

Below is the result:

Answer 1

You don't need nested CASE :

-- multiple conditions
select t.*, case when name = 'abc' and ind = 1 then 1
                 when name = 'abc' and sal > 2000 then 1 
                 else 0 end 
from test t

Answer 2

I don't know why you need nested case expression, i would do instead of nested case expression that would be more efficient :

select t.*, (case when name = 'abc' and (ind = 1 or sal > 2000) 
                  then 1 
                  else 0 
             end) 
from test t;

Answer 3

If you HAVE to have nested case expression then this is how you would write it:

SELECT t.*, 
    CASE 
        WHEN name = 'abc' THEN
            CASE 
                WHEN ind = 1 THEN 1 
                WHEN sal > 2000 THEN 1 
                ELSE 0
            END 
        ELSE 0
    END
FROM test t;

Answer 4

如果您使用的是SQL Server 2012及更高版本，则还可以使用如下所示的IIF语句：

select iif(name = 'abc' AND (salary > 2000 OR ind = 1), 1,0)