PostgreSQL: Select data with a like on timestamp field -

i trying select data table, using "like" on date field "date_checked" (timestamp). have error :

sqlstate[42883]: undefined function: 7 error:  operator not exist: timestamp without time zone

my request :

select my_table.id my_table my_table.date_checker '2011-01-%'

i don't want use :

select my_table.id my_table my_table.date_checker >= '2011-01-01 00:00:00'      ,  my_table.date_checker < '2011-02-01 00:00:00'

it's not "wanting use" < , > timestamps, operators can converted index scans, , string-match... well, can, ewwww.

well, error occurring because need explicitly convert timestamp string before using string operation on it, e.g.:

date_checker::text '2011-01-%'

and suppose create index on (date_checker::text) , expression become index scan but.... ewwww.

Sohocode