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

Question

SELECT id, amount FROM report

I need amount to be amount if report.type=\'P\' and -amount if

Answer 1

select 
  id,
  case 
    when report_type = 'P' 
    then amount 
    when report_type = 'N' 
    then -amount 
    else null 
  end
from table

Answer 2

SELECT id, amount
FROM report
WHERE type='P'

UNION

SELECT id, (amount * -1) AS amount
FROM report
WHERE type = 'N'

ORDER BY id;

Answer 3

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.

Answer 4

SELECT CompanyName, 
    CASE WHEN Country IN ('USA', 'Canada') THEN 'North America'
         WHEN Country = 'Brazil' THEN 'South America'
         ELSE 'Europe' END AS Continent
FROM Suppliers
ORDER BY CompanyName;

Answer 5

You can try this also

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

Answer 6

Use a case statement:

select id,
    case report.type
        when 'P' then amount
        when 'N' then -amount
    end as amount
from
    `report`