'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?

Use a `case` statement:

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

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;

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

UNION

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

ORDER BY id;

Most simplest way is to use a [IF()][1]. Yes Mysql allows you to do conditional logic. IF function takes 3 params CONDITION, TRUE OUTCOME, FALSE OUTCOME.

So Logic is


if report.type = 'p'
amount = amount
else
amount = -1*amount

**SQL**

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


You may skip abs() if all no's are +ve only

[1]:

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

You can try this also

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

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

See

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.

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*.