Microsoft SharePoint Team Blog
The official blog of the Microsoft SharePoint Product Group

Creating an Identity Column Using SQL



If you are programmatically creating a column, to indicate that it would be used as an identity column after its name and data type, type identity followed by parentheses. Between the parentheses, enter the seed value, followed by a comma, followed by the increment value. Here is an example:

CREATE TABLE StoreItems(
ItemID int IDENTITY(1, 1) NOT NULL,
Category varchar(50),
[Item Name] varchar(100) NOT NULL,
Size varchar(20),
[Unit Price] money);
GO
Functions and Data Entry


Introduction



You can involve a function during data entry. As an example, you can call a function that returns a value to assign that value to a column. You can first create your own function and use it, or you can use one of the built-in functions.

Using Functions



In order to involve a function with your data entry, you must have and identity one. You can use one of the built-in functions of Transact-SQL. You can check one of the functions we reviewed in Lesson 7. Normally, the best way is to check the online documentation to find out if the assignment you want to perform is already created. Using a built-in function would space you the trouble of getting a function. For example, imagine you have a database named AutoRepairShop and imagine it has a table used to create repair orders for customers:

CREATE TABLE RepairOrders
(
RepairID int Identity(1,1) NOT NULL,
CustomerName varchar(50),
CustomerPhone varchar(20),
RepairDate DateTime
);
GO
When performing data entry for this table, you can let the user enter the customer name and phone number. On the other hand, you can assist the user by programmatically entering the current date. To do this, you would call the GETDATE() function. Here are examples:

INSERT INTO RepairOrders(CustomerName, CustomerPhone, RepairDate)
VALUES('Annette Berceau', '301-988-4615', GETDATE());
GO
INSERT INTO RepairOrders(CustomerPhone, CustomerName, RepairDate)
VALUES('(240) 601-3795', 'Paulino Santiago', GETDATE());
GO
INSERT INTO RepairOrders(CustomerName, RepairDate, CustomerPhone)
VALUES('Alicia Katts', GETDATE(), '(301) 527-3095');
GO
INSERT INTO RepairOrders(RepairDate, CustomerPhone, CustomerName)
VALUES(GETDATE(), '703-927-4002', 'Bertrand Nguyen');
GO
You can also involve the function in an operation, then use the result as the value to assign to a field. You can also call a function that takes one or more arguments; make sure you respect the rules of passing an argument to a function when calling it.

If none of the Transact-SQL built-in functions satifies your requirements, you can create your own, using the techniques we studied in Lesson 6.

Using Expressions For Data Entry


Introduction



There are various ways you can assist the user with data entry. Besides using a function, you can create an expression using operators such as those we reviewed in lessons 3 and 5. You can create an expression when creating a table, whether in the Table window or using SQL in a query window.

Visually Creating an Expression



To create an expression when visually creating a table, in the top section, specify the column's name (only the column name is important). In the bottom section, expand the Computed Column Specification field and, in its (Formula) field, enter the desired expression.




source : http://blogs.msdn.com/sharepoint/default.aspx