how to remove the duplicate records from a table

[Yi Zhao <yi.zhao@xxxxxxxxxxxxxxx>]

I have a table contains some duplicate records, and this table create
without oids, for example:
 id | temp_id 
----+---------
 10 |       1
 10 |       1
 10 |       1
 20 |       4
 20 |       4
 30 |       5
 30 |       5
I want get the duplicated records removed and only one is reserved, so
the results is:
10 1
20 4
30 5

I know create a temp table will resolve this problem, but I don't want
this way:)

can someone tell me a simple methold?

any help is appreciated,

thanks,