MySQL IF NOT NULL, then display 1, else display 0
SELECT c.name, IF(a.addressid IS NULL,0,1) AS addressexists
FROM customers c
LEFT JOIN addresses a ON c.customerid = a.customerid
WHERE customerid = 123
Careful if you're coming from C/C++ and expecting this to work:
select if(name, 1, 0) ..
Even if 'name' is not NULL, unlike in C, a false-condition still triggers and the above statement returns 0. Thus, you have to remember to explicitly check for NULL or empty string:
select if(name is null or name = '', 0, 1)
PS Eugen's example up above is correct, but I wanted to clarify this nuance as it caught me by surprise.
Instead of COALESCE(a.addressid,0) AS addressexists
, use CASE
:
CASE WHEN a.addressid IS NOT NULL
THEN 1
ELSE 0
END AS addressexists
or the simpler:
(a.addressid IS NOT NULL) AS addressexists
This works because TRUE
is displayed as 1
in MySQL and FALSE
as 0
.