Question

I have this kind of simple query that returns a not null integer field for a given id:

SELECT field1 FROM table WHERE id = 123 LIMIT 1;

The thing is if the id is not found, the resultset is empty. I need the query to always return a value, even if there is no result.

I have this thing working but I don’t like it because it runs 2 times the same subquery:

SELECT IF(EXISTS(SELECT 1 FROM table WHERE id = 123) = 1, (SELECT field1 FROM table WHERE id = 123 LIMIT 1), 0);

It returns either field1 if the row exists, otherwise 0. Any way to improve that?

Thanks!

Edit following some comments and answers: yes it has to be in a single query statement and I can not use the count trick because I need to return only 1 value (FYI I run the query with the Java/Spring method SimpleJdbcTemplate.queryForLong()).

Answer 1

MySQL has a function to return a value if the result is null. You can use it on a whole query:

SELECT IFNULL( (SELECT field1 FROM table WHERE id = 123 LIMIT 1) ,'not found');