mysql - 如何改变空结果？mysql

Question

SELECT 'id'  FROM `table` WHERE `id` = 
(select min(`id`) FROM `table` where 
`id` < 1 and `ids` = 1)

id       ids
1         1
2         1
5         1
6         1

结果：

id = ''

我需要更改id=''为id='n/a'

Answer 1

If the query return a null result you can use COALESCE so :

SELECT COALESCE('id','N/A') FROM ...

OR if the return result is an empty string you can do :

SELECT CASE WHEN id = '' THEN 'N/A' ELSE id END FROM ...

Answer 2

Another option would be: IFNULL