An interview question record about where in MySQL

problem

select id from test where is_deleted

This article sql Will find out what data

answer

If your is_deleted The fields are int type , So long as it is not 0 perhaps null, Will be found out , What I'm talking about is null, Not empty

If your is_deleted The fields are varchar perhaps char, Then its must have a value in and begin with a number and not be 0 It can only be found out if