Same primary key in a table

Asked Jun 09 '14 at 05:19

Active Jun 09 '14 at 05:19

Viewed 91 times

I just started learning SQL in a book, and I'm stack at understanding the concept of the primary key.

Here I have to explain little about these tables in this db.

The Order table stores customer orders but not order details. Each order is uniquely numbered.

The orderItems table stores the actual items in each order, one row per item per order.

I thought primary key could be used for the identical column in a table, and same values couldn't be inserted. But I found couple of the same values are inserted in the primary key(order_num, order_items) in orderItems

enter image description here

asked Jun 09 '14 at 05:19

Toshi

6,012
8
35
58

Take a look at the concept of a "composite key". – Tetsujin no Oni Jun 09 '14 at 05:22
It's called a composite primary key, please see http://stackoverflow.com/questions/217945/can-i-have-multiple-primary-keys-in-a-single-table – 3dd Jun 09 '14 at 05:22

Same primary key in a table

0 Answers0