我怎样才能在mysql中编写IF语句

Question

I have a table with type field.

how can I check this field in query:

I want to check it if type == 'a'

then bes = amount , bed = '-'

ELSE bed = amount , bes = '-'

bes and bed is not really exists in my table but amount is (int)

this is my try:

SELECT billing.*,
    CASE billing.type WHEN 'A' THEN billing.amount AS bes, '-' AS bed ELSE billing.amount AS bed, '-' AS bes END
    FROM billing

... my searches wasn't useful

any solution...

Answer 1

You can create condition for every row, MySQL supports inline IF statements.

SELECT billing.*,
       IF(billing.type = 'A', billing.amount, '-') AS bes,
       IF(billing.type = 'A', '-', billing.amount) AS bed
FROM   billing

Answer 2

You'll need two case statements for that:

SELECT billing.*,
  CASE billing.type WHEN 'A' THEN billing.amount ELSE '-' AS bes END,
  CASE billing.type WHEN 'A' THEN '-' ELSE billing.amount AS bed END
FROM billing

Answer 3

One CASE-WHEN-THEN-ELSE can have only one return value...

This should do the trick:

SELECT billing.*,
CASE billing.type WHEN 'A' THEN billing.amount ELSE '-' END AS bes,
CASE billing.type WHEN 'A' THEN '-' ELSE billing.amount END AS bed 
FROM billing

Answer 4

SELECT billing.*,
    CASE  WHEN billing.type =  'A' THEN billing.amount ELSE 0 END AS bes,
    CASE  WHEN billing.type <> 'A' THEN billing.amount ELSE 0 END AS bed
FROM billing

Answer 5

Depending on your MySQL version, you can use IF or one of two different syntaxes for CASE CASE (1), CASE (2).

SELECT *,
  (IF type = 'A' THEN amount ELSE '-' END IF) bes,
  (IF type = 'A' THEN '-' ELSE amount END IF) bed
FROM billing