If else on WHERE clause

Question

I\'ve this query:

SELECT  `id` ,  `naam` 
FROM  `klanten` 
WHERE (
`email` LIKE  \'%@domain.nl%\'
OR  `email2` LIKE  \'%@domain.nl%\'
)

But

Answer 1

Note the following is functionally different to Gordon Linoff's answer. His answer assumes that you want to use email2 if email is NULL. Mine assumes you want to use email2 if email is an empty-string. The correct answer will depend on your database (or you could perform a NULL check and an empty-string check - it all depends on what is appropriate for your database design).

SELECT  `id` ,  `naam` 
FROM  `klanten` 
WHERE `email` LIKE  '%anja@fiskkoer.nl%'
OR (LENGTH(email) = 0 AND `email2` LIKE  '%anja@fiskkoer.nl%')