Question

When I send query like

SELECT id FROM private_messages WHERE to_id=1 AND opened=0

It doesn’t return anything

SELECT id FROM private_messages WHERE to_id=1 AND opened<>1

Returns all results where opened=0. opened columns type is enum with “1” and “0” (default) values. Question is, why first query doesn’t return anything?

Answer 1

Since opened is an enum, you should write:

SELECT id FROM private_messages WHERE to_id=1 AND opened='0'

Enums are really just a set of possible strings. From the documentation:

An ENUM is a string object with a value chosen from a list of
permitted values that are enumerated explicitly in the column
specification at table creation time.