if exists / where exisyts....

i want to test if a table exists before to drop this......

the :
if exists (select 1 from pg_tables where tablename = "thetable")
drop table thetable
;

don't work....

i try :

wher e exists (....)
;

don't work.


but the expresssion :
select * from pg_tables where exists(select 1 from pg_tables where 
tablename = "thetable")
;

work