T-SQL Transact-SQL is microsoft implementation of SQL. It contains additional programming constracts T-SQL enables you to write programs that contain SQL statements.

Using Variables You can declare variable using DECLARE statement, followed by the variable name and the type type For example nvarchar(40) int

Using Variables Variables are initially set to null. You set a variables’ value using SET statement ‘Chai’ = 7 The following SELECT statement uses these variables: Select ProductId, ProductName, UnitPrice From Products Where OR

Using Conditional Logic T-SQL enables you to use conditional logic operaters in SQL stataments. IF-then-ELSE IF conditon statement 1 ELSE statement 2 You can replace a single statement with multiple statements by placing those statements within BEGIN and END statements

Using Conditional Logic If (Select Count(*) from products where unitprice 0 BEGIN Print ‘The following products have a UnitPrice of less than 5’ Select ProductId, ProductName, UnitPrice From Products Where UnitPrice<5 END Else BEGIN Print ‘There are no products that have a UnitPrice of less than 5’ END

Using CASE Statement The following example uses a select statement to retrieve the value Massachusetts returned by the case statement: nchar(2) =‘MA’ nvarchar(15) Select as State When ‘CA’ then ‘California’ When ‘MA’ then ‘Massachusetts’ When ‘NY’ then ‘New York’ End

Using CASE Statement You can store the value retrived by the SELECT statement in a variable as shown in the example nchar(2) =‘MA’ nvarchar(15) When ‘CA’ then ‘California’ When ‘MA’ then ‘Massachusetts’ When ‘NY’ then ‘New York’ End

Using CASE Statement You can also compare a column value in a CASE statement Select Price= Case When UnitPrice is NULL then 'Unknown' When UnitPrice <10 then 'Less than 10' When UnitPrice =10 then '10' Else 'Greater than 10' End From Products

While Loops While conditon statement The following example shows a while loop: int = 5 While Begin Print ‘count=’ + Set End

Continue Statement You can use the Continue statement to start a next iteration of while loop immediately, skipping over any remaining code in the loop. int = 5 While Begin Print ‘count=’ + Set if Begin Set Continue end End

Break Statement int = 5 While Begin Print ‘count=’ + Set If Begin Break End

Using Labels and the Goto Statement You use the Goto statement to jump a specified label in your code; you use a label to identify a statement of your code. int = 5 myLabel: Print ‘count=’ + Set If Begin GOTO myLabel End Output of these code is the same with the while loop’s output

Using Waitfor Statement There are times when you want your program to pause before running some code to perform a specific action, such as running a batch program at night to update customer records WAITFOR {DELAY ‘ time interval’ | TIME ‘actual time’} Waitfor Delay ‘00:00:05’ waits for a time interval of 5 seconds

Using Waitfor Statement Using WAITFOR TIME: The following example executes the stored procedure sp_update_job at 10:20 P.M. (22:20). USE msdb; EXECUTE = 'TestJob'; BEGIN WAITFOR TIME '22:20'; EXECUTE = = 'UpdatedJob'; END; GO

Using Waitfor Statement Using WAITFOR DELAY: The following example executes the stored procedure after a two-hour delay. BEGIN WAITFOR DELAY '02:00'; EXECUTE sp_helpdb; END; GO

Using Raiserror Statement You use the Raiserror statement to generate an error message. It is typically used to if an error is occurs in one of your stored procedures. Syntax: RAISERROR({number | description}{, severity, state}) Number is error number and between 50,001 and 2,147,483,648 Description is the error message Severity is the degree of the error and between 0 and 18

Using Raiserror Statement The following code example shows how to use RAISERROR inside a TRY block to cause execution to jump to the associated CATCH block. It also shows how to use RAISERROR to return information about the error that invoked the CATCH block. BEGIN TRY -- RAISERROR with severity will cause execution to -- jump to the CATCH block. RAISERROR ('Error raised in TRY block.', -- Message text. 16, -- Severity State. ); END TRY BEGIN CATCH NVARCHAR(4000); INT; INT; = = = ERROR_STATE(); -- Use RAISERROR inside the CATCH block to return error -- information about the original error that caused -- execution to jump to the CATCH block. RAISERROR -- Message State. ); END CATCH;

Using Cursor When you execute a SELECT statement, all the effected rows are returned in one go. Sometimes you might want to take some action based on the column values retrived for a particular row. To do this, you can use a cursor to process rows retrived from the database one row at a time.

Using Cursor You follow these steps when using a cursor: Declare Variables to Store the Column Values from the Select Statement These variables must be compatible with the column types for the retrieved rows. Example: int nvarchar (40) money

Using Cursor Declare the Cursor A cursor declaration consists of a name that you assign to the cursor and a SELECT statement that you want to execute retrieved rows. This SELECT statement is not actually run until you open the cursor. Example: DECLARE ProductCursor CURSOR for Select ProductID, ProductName, UnitPrice from Products Where ProductID<=10

Using Cursor Open the Cursor You open a cursor using the OPEN statement. OPEN ProductCursor Fetch the Rows from the Cursor To read each row from your cursor, use the fetch statement Since there might be many rows, you need to usee While loop. To check end of loop, use function. This function returns: 0 if FETCH statement successfully returned a row. -1if FETCH statement failed or the requested row is outside the result set. -2 if Row fetched is missing

Using Cursor The following example shows a loop that reads each row from ProductCursor. Fetch Next from @MyUnitPrice Print + Convert Print + Convert Print + Convert While Begin Fetch Next from @MyUnitPrice Print + Convert Print + Convert Print + Convert END

Using Cursor Close the Cursor You close a cursor using the CLOSE statement. CLOSE ProductCursor You should also remoce the reference to your curs or using the DEALLOCATE statement. DEALLOCATE ProductCursor

Functions There are many built-in functions to use in T- SQL. You can find detailed explanation about these functions from the web site below: us/library/ms aspx

Creating User-Defined Functions You create a function using the CREATE FUNCTION statement. There are three types of user-defined functions: Scalar Functions: These functions returns a single value. Inline Table-valued Functions: Returns an object of the table type. You can think of a table a a regular database table, except it is stored in memory. An inline table-valued function can return the results retrived by only a single SELECT statement. Multistatement table-valued Function: Returns a object of table type and it can contain multiple T- SQL statement.

Creating User-Defined Functions Scalar Functions: The example below creates the DiscountPrice() function, which returns the original price of an item multipled by a discount factor. Create Function money) Returns Money As Begin End Using this function: Float =0.3 Select ), UnitPrice From Products Where ProductID=1

Creating User-Defined Functions Inline Table-Valued Functions: Inline user- defined functions are a subset of user-defined functions that return a table. Inline functions can be used to achieve the functionality of parameterized views. Consider this view: CREATE VIEW vw_CustomerNamesInWA AS SELECT CustomerID, CompanyName FROM Northwind.dbo.Customers WHERE Region = 'WA'

Creating User-Defined Functions Inline Table-Valued Functions: You can create a more generalized version, vw_CustomerNamesInRegion, by replacing the WHERE Region = 'WA' with a WHERE Region and letting users specify the region they are interested in viewing. Views, however, do not support parameters in the search conditions specified in the WHERE clause.

Creating User-Defined Functions CREATE FUNCTION fn_CustomerNamesInRegion nvarchar(30) ) RETURNS table AS RETURN ( SELECT CustomerID, CompanyName FROM Northwind.dbo.Customers WHERE Region ) -- Example of calling the function for a specific region SELECT * FROM fn_CustomerNamesInRegion(N'WA')

Creating User-Defined Functions Inline user-defined functions follow these rules: The RETURNS clause contains only the keyword table. You do not have to define the format of a return variable because it is set by the format of the result set of the SELECT statement in the RETURN clause. There is no function_body delimited by BEGIN and END. The RETURN clause contains a single SELECT statement in parentheses. The result set of the SELECT statement forms the table returned by the function. The SELECT statement used in an inline function is subject to the same restrictions as SELECT statements used in views. The table-valued function accepts only constants arguments

Creating User-Defined Functions Inline Table-Valued Functions: The example below creates the ProductsToBeReordered() function, which returns a table containing the rows from the Products table Create Function ProductsToBeReordered int) Returns Table As Return ( Select * From Products Where ) Using this function: Select ProductID, ProductName, UnitsInStock From ProductsToBeReordered(10) Where ProductId<=50;

Creating User-Defined Functions Multistatement Table-Valued Functions: User-defined functions that return a table can be powerful alternatives to views. A user-defined function that returns a table can be used where table or view expressions are allowed in Transact-SQL queries. While views are limited to a single SELECT statement, user-defined functions can contain additional statements that allow more powerful logic than is possible in views. In a user-defined function that returns a table: The RETURNS clause defines a local return variable name for the table returned by the function. The RETURNS clause also defines the format of the table. The scope of the local return variable name is local within the function. The Transact-SQL statements in the function body build and insert rows into the return variable defined by the RETURNS clause. When a RETURN statement is executed, the rows inserted into the variable are returned as the tabular output of the function. The RETURN statement cannot have an argument.

Creating User-Defined Functions This example creates a function in the Northwind database that returns a table: CREATE FUNCTION LargeOrderShippers money ) TABLE ( ShipperID int, ShipperName nvarchar(80), OrderID int, ShippedDate datetime, Freight money ) AS BEGIN SELECT S.ShipperID, S.CompanyName, O.OrderID, O.ShippedDate, O.Freight FROM Shippers AS S INNER JOIN Orders AS O ON S.ShipperID = O.ShipVia WHERE O.Freight RETURN END This query references the table returned by the function in its FROM clause: SELECT * FROM LargeOrderShippers( $500 )

Creating User-Defined Functions Multistatement Table-Valued Functions: The example below creates the ProductsToBeReordered2() function, which returns a table containing the rows from the Products table Create Function ProductsToBeReordered2 int) table ( ProductID int, ProductName nvarchar(40), UnitsInStock smallint, Reorder nvarchar(3) ) As Begin Insert Select ProductID, ProductName, UnitsInStock, ‘no’ from Products Set Reorder=‘yes’ Where Return End Usage of the function Select * from ProductsToBeReordered2(20)