Return 0 if field is null in MySQL

Solution 1:

Use IFNULL:

IFNULL(expr1, 0)

From the documentation:

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.

Solution 2:

You can use coalesce(column_name,0) instead of just column_name. The coalesce function returns the first non-NULL value in the list.

I should mention that per-row functions like this are usually problematic for scalability. If you think your database may get to be a decent size, it's often better to use extra columns and triggers to move the cost from the select to the insert/update.

This amortises the cost assuming your database is read more often than written (and most of them are).

Solution 3:

None of the above answers were complete for me. If your field is named field, so the selector should be the following one:

IFNULL(`field`,0) AS field

For example in a SELECT query:

SELECT IFNULL(`field`,0) AS field, `otherfield` FROM `mytable`

Hope this can help someone to not waste time.