Michael Michael - 4 months ago 8
MySQL Question

'IF' in 'SELECT' statement - choose output value based on column values

SELECT id, amount FROM report


I need
amount
to be
amount
if
report.type='P'
and
-amount
if
report.type='N'
. How do I add this to the above query?

Answer
SELECT 
        id
        , IF(type = 'P', amount, amount * -1) as amount
FROM    report

See http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html.

Additionally, you could handle when the condition is null. In the case of a null amount:

SELECT 
        id
        , IF(type = 'P', IFNULL(amount,0), IFNULL(amount,0) * -1) as amount
FROM    report

The part IFNULL(amount,0) means when amount is not null return amount else return 0.