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Monday, December 5, 2016

How to Insert data into a table with Identity column

In general, you don't insert data manually in a table which has an identity column. However, in obvious cases if you need to insert data into the table manually then writing general inset Query will failed with error:

For example, you have a table (DDL) like below:
  Create table PurchaseOrder
   (orderId int identity(1,1),
    item nvarchar(100))

If you would like to insert data into the table, standard syntax for inserting data is like below:

    Insert into PurchaseOrder(orderId,item)
     values (101,'strawberry')


However, above query will failed with below error message:

Fig 1: Eror Inserting data into the table with Identiy column

To insert the data into a table with identity column you should not put any value for the identity column. e.g. 

Insert into PurchaseOrder (orderId,item)
values ('strawberry')  

And then you will see the result set like below:


Fig 2. Output of the above insert command

However, if you would like to explicity put value for the identity column. e.g. you would like to add a negative number as orderid to make an item invalid. (sometimes you may need for the data warehouse dimension and fact tables). SQL for inserting data with your own choice:

SET IDENTITY_INSERT PurchaseOrder ON
insert into PurchaseOrder(orderId,item)
values (-1,'An Island')
SET IDENTITY_INSERT PurchaseOrder OFF


Now the result will look like below:

Fig 3: Output after  the above SQL command




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