two auto increment fields

alirezaok

i need two auto increment fields in one table. it is not possible?

jheitz

What do you need them for?... that is quite odd really. After all, if they are both auto-incremental (let's say field A and 😎 that means that one of them equals the other plus an offset doesn't it? And if that is so, then you don't really need 2 auto increment fields.

Please give us more details so we might be able to assist. Also: which database system are you using?

alirezaok

thanks, I am using of mysql.

i need for it because in the future the records of field B change and will update. then records of two fields will not be equal.

NogDog

MySQL only allows one column in a table to be defined as auto-increment.

You could define a 2-step process, I suppose:

// assume id1 is the primary key and auto-incremented:
mysql_query("INSERT INTO table (id1, id2, data) VALUES (NULL, 0, 'some data')");
$number = mysql_insert_id();
mysql_query("UPDATE table SET id2=$number WHERE id1=$number");

Piranha

If you are even more advanced you can do it in a trigger if you use MySQL 5 or later. But you have to read up on that yourself, I have never used them in MySQL.

tomhath

alirezaok wrote:
i need for it because in the future the records of field B change and will update. then records of two fields will not be equal.

Then you don't need it, because you cannot change the value of an auto-increment field. It's set when the row is inserted and never changed.