SQL Server - Understanding full power of CASE Expressions

Many programming languages like VB6 support IIF function which is used to return a value based on a particular expression/condition. In SQL Server the equivalent is to make use of CASE Expression, which is used to evaluate many conditions and return a single value. The following examples will give you some ideas on how to use CASE expression effectively

declare @t table(emp_id int, emp_name varchar(100), sex char(1))
insert into @t
select 1,'Suresh','M' union all
select 1,'John','M' union all
select 1,'Clara','F'

1 Set Male or Female based on the value of sex

select emp_id,emp_name,
case
when sex='M' then 'Male'
when sex='F' then 'Female'
end as sex
from
@t

Result:

emp_id      emp_name           sex
----------- --------------     -----
1           Suresh             Male
1           John               Male
1           Clara              Female

Read more: Beyond Relational

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