altering a table to set serial function

Dear my friends... I am using postgres 7.4 and SuSE 9.1. I want to use auto_increment as on MySQL. I look up the documentation on www.postgres.com and I found "serial" . But I don't know how to create auto_increment. here is my try: " kv=# alter table sales alter column salesid int4 serial; ERROR: syntax error at or near "int4" at character 40 " Please tell me the correct command to that. Thank you very much in advance. __________________________________ Do you Yahoo!? Read only the mail you want - Yahoo! Mail SpamGuard. http://promotions.yahoo.com/new_mail