I am newbie in My Sql. Can somebody tell me how can I set two primary keys in a table? I set PRIMARY KEY (id1,id2) but it works like there are set as two different keys and not like one. I tried to add id1=1 id2=2 and id1=1 id2=3 but My Sql reurned an error

what does "it works like there are set as two different keys and not like one" mean?

can you show the CREATE TABLE statement?

when you say 2 primary keys
do you mean 1 primary and 1 unique key (ie 2 separate columns) - although this would suggest your data model is invalid and carrying redundant information.
OR 1 Primary key that is a composite of 2 columns?

The problem solved by itself. Thank you very much. the table was
CREATE TABLE `price` (
`barcode` smallint(15) NOT NULL default '0',
`shop_id` smallint(6) NOT NULL default '0',
`price` double(15,2) default NULL,
PRIMARY KEY (`barcode`,`shop_id`)
) TYPE=MyISAM

My friend thank you very much for the reply. the problem got solved. I don't know how. When I say two primary keys I mean two columns that form One primary key. It is used for many to many relationships. Thank you again

me neither