SQLite - Get timestamp column as long discarding the time and in local time in Android

I have a column in a table which type is long to store unix time using:

DEFAULT CURRENT_TIMESTAMP

Then I get local timestamp by doing:

select datetime(timestamp,'localtime') from ...

I get something like:

"2015-01-18 22:13:52"

but I would like to obtain this (discarding the time):

"2015-01-18 00:00:00"

but not in string type but in long type.