Apr 24, 2007 Identity Columns - An identity is a common 'auto generated' primary key to use in a SQL Server database these days. An identity is simply an integer value that 'auto increments' as each new row is added to your table. You can specify when it should start and how it should increment when you add the column to your table. The ID that was generated is maintained in the server on a per-connection basis. This means that the value returned by the function to a given client is the first AUTOINCREMENT value generated for most recent statement affecting an AUTOINCREMENT column by that client. Apr 15, 2013 I am wanting to use a Guid (uniqueidentifier) as my primary key in my table. I want the server to generate it automatically when I insert into the table. Primary Key Generation Using SQL Server's IDENTITY. In SQL Server you can use the IDENTITY keyword to indicate that a primary-key needs to be auto-generated. The following example shows a common scenario where the first primary key value is 1, and the increment is 1.
- Sql Server Auto Generated Primary Key Mean
- Sql Server Auto Increment Non Primary Key
- Sql Server Auto Generated Primary Key Definition
You can define a primary key in SQL Server by using SQL Server Management Studio or Transact-SQL. Creating a primary key automatically creates a corresponding unique clustered index, or a nonclustered index if specified as such.
Before You Begin
Limitations and Restrictions
- A table can contain only one PRIMARY KEY constraint.
- All columns defined within a PRIMARY KEY constraint must be defined as NOT NULL. If nullability is not specified, all columns participating in a PRIMARY KEY constraint have their nullability set to NOT NULL.
Security
Permissions
Creating a new table with a primary key requires CREATE TABLE permission in the database and ALTER permission on the schema in which the table is being created.
Creating a primary key in an existing table requires ALTER permission on the table.
Using SQL Server Management Studio
To create a primary key
- In Object Explorer, right-click the table to which you want to add a unique constraint, and click Design.
- In Table Designer, click the row selector for the database column you want to define as the primary key. If you want to select multiple columns, hold down the CTRL key while you click the row selectors for the other columns.
- Right-click the row selector for the column and select Set Primary Key.
Caution
If you want to redefine the primary key, any relationships to the existing primary key must be deleted before the new primary key can be created. A message will warn you that existing relationships will be automatically deleted as part of this process.
A primary key column is identified by a primary key symbol in its row selector.
If a primary key consists of more than one column, duplicate values are allowed in one column, but each combination of values from all the columns in the primary key must be unique.
If you define a compound key, the order of columns in the primary key matches the order of columns as shown in the table. However, you can change the order of columns after the primary key is created. For more information, see Modify Primary Keys.
Using Transact-SQL
To create a primary key in an existing table
The following example creates a primary key on the column
TransactionID
in the AdventureWorks database.Sql Server Auto Generated Primary Key Mean
To create a primary key in a new table
The following example creates a table and defines a primary key on the column
TransactionID
in the AdventureWorks database.Sql Server Auto Increment Non Primary Key
To create a primary key with clustered index in a new table
The following example creates a table and defines a primary key on the column
CustomerID
and a clustered index on TransactionID
in the AdventureWorks database.