Why does MySQL not use an index on a int field that's being used as a boolean?

Question

select * from myTable where myInt

will not show any possible_keys when explaining the query even though there is an index on myInt field.

Edit:
The index in question is not unique.

Answer 1

For MySQL to use the index, you have to explicitly compare the int field to a value (e.g. true, 1).

select * from myTable where myInt = true