We can not directly change a column to identity columns, say we have a primary key column or any normal column in our table and want to make it identity column then we cannot do it directly by altering the table but there are only two way to change column to identity column
These are the case if we can not open our database in SQL Server Management Studio if we can then
Now let's back to our previous point that if we cannot see our table in design view then
1. Create a new table with same structure and identity column and copy existing table records to this table and drop the existing table
In this approach we can save our existing IDs as it is, suppose we have a table named Tags without identity then we can create a table Tags1 with same column but with Identity column like this
CREATE TABLE [Tags1] ( [TagID] [smallint] IDENTITY(1,1) NOT NULL, [TagName] [varchar](50) NOT NULL, [Count] [int] NULL, )
Now write the script to copy the data from Tags table to Tags1
SET IDENTITY_INSERT [dbo].[Tags1] ON Go INSERT INTO [dbo].[Tags1] ( [TagID], [TagName], [Count] ) SELECT [TagID], [TagName], [Count] FROM [dbo].[Tags] Go SET IDENTITY_INSERT dbo].[Tags1] OFF
Now we get every thing in our new table Tags1 so time to drop our old table Tags and rename Tags1 to Tags
DROP TABLE dbo].[Tags] Go EXEC sp_rename 'Tags1', 'Tags' Go
Now our Tags table have identity column as well as our previous records as well.
2. Add new column to table with identity and drop the existing column
ALTER TABLE Tags ADD TagID1 INT IDENTITY(1,1) Go ALTER TABLE Tags DROP COLUMN TagID Go EXEC sp_rename 'Tags.TagID1', 'TagID', 'COLUMN' Go
This way of adding new column and dropping existing one and finally renaming new column name to old column name is easy but in this way we cannot save our existing data (IDs).
Having 13+ years of experience in Microsoft Technologies (C#, ASP.Net, MVC and SQL Server). Worked with Metaoption LLC, for more than 9 years and still with the same company. Always ready to learn new technologies and tricks.
|By Ali Adravi On 02 May, 13 Viewed: 660|
There are many ways which can help us to save our time to write some repeated code or to do some repeated action, in this post we will see some very common code which we need very frequently in our development life. I am not saying that after this post you will save your half say work every day but... By Ali Adravi On 31 Mar 2013 Viewed: 712
In SQL server there are decimal and money data type to store precision and scale both together or say decimal values. Suppose we want to get precision and scale separately then how to get it. There are many ways to do this but there is a function in SQL named PARSENAME which can be used to get... By Myghty On 26 Mar 2013 Viewed: 1,889
To write a good performing procedure or function we should be aware about available wildcards in SQL Server. I found most developer depends on ‘%’ wildcard only while we have others as well. In this article we will discuss all the available wildcards in detail with examples. First of all let’s see... By Dev D On 25 Feb 2013 Viewed: 482
When we need to concatenate two columns simply we can use `+` sign and that is correct, but what if any of them is null, Will it return what we want, NO, it will return null. So let's discuss how we should concatenate two or more columns without creating extra space or extra comma problem. Let's... By Ali Adravi On 13 Feb 2013 Viewed: 9,134
TRY…CATCH constructs do not trap the following conditions: - Warnings or informational messages that have a severity of 10 or lower. - Errors that have a severity of 20 or higher those stop the SQL Server Database Engine task processing for the session. If an error occurs that has severity of... By Ali Adravi On 28 Dec 2012 Viewed: 464