Using OUTPUT Parameters in Stored Procedures

According to MS-BOL, SQL Server Stored-Procedures can return data in 4 forms:
1. Return Code: which are always an integer value.
2. OUTPUT Parameter: which can return either data (such as an integer or character value) or a cursor variable (cursors are result sets that can be retrieved one row at a time).
3. A result set for each SELECT statement contained in the stored procedure or any other stored procedures called by the stored procedure.
4. A global cursor that can be referenced outside the stored procedure.

Specifying OUTPUT keyword to the parameters in the Stored Procedures can return the values of the parameters to the calling program. Lets check this with a simple example by using AdventureWorks database:

USE [AdventureWorks]
GO

--// Create Stored Prcedure with OUTPUT parameter
CREATE PROCEDURE getContactName
	@ContactID INT,
	@FirstName VARCHAR(50) OUTPUT,
	@LastName  VARCHAR(50) OUTPUT
AS
BEGIN
	SELECT @FirstName = FirstName, @LastName = LastName
	FROM Person.Contact
	WHERE ContactID = @ContactID
end
GO

--// Test the Procedure
DECLARE @CID INT, @FName VARCHAR(50), @LName VARCHAR(50)

--/ Test# 1
SET @CID = 100
EXEC getContactName @ContactID=@CID,
					@FirstName=@FName OUTPUT,
					@LastName=@LName OUTPUT

SELECT @FName as 'First Name', @LName as 'Last Name'
--/ Output
-- ContactID	First Name	Last Name
-- 100			Jackie		Blackwell

--/ Test# 2
SET @CID = 200
EXEC getContactName @ContactID=@CID,
					@FirstName=@FName OUTPUT,
					@LastName=@LName OUTPUT

SELECT @FName as 'First Name', @LName as 'Last Name'
--/ Output
-- ContactID	First Name	Last Name
-- 200			Martin		Chisholm
GO

--// Final Cleanup
DROP PROCEDURE getContactName
GO

MDSN Links: http://msdn.microsoft.com/en-us/library/aa214332(v=SQL.80).aspx

UDF | User Defined Functions – Scalar, ITV, MTV

UDF or User Defined Functions are a set or batch of code where one can apply any SQL logic and return a single scalar value or a record set.

According to MS BOL UDFs are the subroutines made up of one or more Transact-SQL statements that can be used to encapsulate code for reuse. These reusable subroutines can be used as:
- In TSQL SELECT statements at column level.
- To create parametrized view or improve the functionality of in indexed view.
- To define a column and CHECK constraints while creating a table.
- To replace a stored procedures and views.
- Join complex logic with a table where a stored procedure fails.
- Faster execution like Stored procedures, reduce compliation cost by caching the execution query plans.

Apart from the benefits UDF’s has certain limitations:
- Can not modify any database objects, limited to update table variables only.
- Can not contain the new OUTPUT clause.
- Can only call extended stored procedures, no other procedures.
- Can not define TRY-CATCH block.
- Some built-in functions are not allowed here, like:GETDATE(), because GETDATE is non-deterministic as its value changes every time it is called. On the other hand DATEADD() is allowed as it is deterministic, because it will return same result when called with same argument values.

A UDF can take 0 or upto 1024 parameters and returns either a scalar value or a table record set depending on its type.
SQL Server supports mainly 3 types of UDFs:
1. Scalar function
2. Inline table-valued function
3. Multistatement table-valued function

1. Scalar function: Returns a single value of any datatype except text, ntext, image, cursor & timestamp.

-- Example:
--// Create Scalar UDF [dbo].[ufn_GetContactOrders]
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[ufn_GetContactOrders](@ContactID int)
RETURNS varchar(500)
AS
BEGIN
	DECLARE @Orders varchar(500)

	SELECT @Orders = COALESCE(@Orders + ', ', '') + CAST(SalesOrderID as varchar(10))
	FROM Sales.SalesOrderHeader
	WHERE ContactID = @ContactID

	RETURN (@Orders)
END

--// Usage:
-- Used at COLUMN level with SELECT
SELECT ContactID, dbo.ufn_GetContactOrders(ContactID) FROM Person.Contact
WHERE ContactID between 100 and 105 -- Output below

-- Used while defining a computed column while creating a table.
CREATE TABLE tempCustOrders (CustID int, Orders as (dbo.ufn_GetContactOrders(CustID)))

INSERT INTO tempCustOrders (CustID)
SELECT ContactID FROM Person.Contact
WHERE ContactID between 100 and 105

SELECT * FROM tempCustOrders -- Output below

DROP TABLE tempCustOrders

Output of both the selects above:
ContactID	OrdersCSV
100		51702, 57021, 63139, 69398
101		47431, 48369, 49528, 50744, 53589, 59017, 65279, 71899
102		43874, 44519, 46989, 48013, 49130, 50274, 51807, 57113, 63162, 69495
103		43691, 44315, 45072, 45811, 46663, 47715, 48787, 49887, 51144, 55310, 61247, 67318
104		43866, 44511, 45295, 46052, 46973, 47998, 49112, 50215, 51723, 57109, 63158, 69420
105		NULL

Note: If this was a temp(#) table then the function also needs to be created in tempdb, cause the temp table belongs to tempdb. The tables in function should also have the database name prefixed, i.e. [AdventureWorks].[Sales].[SalesOrderHeader]

2. Inline table-valued function: Returns a table i.e. a record-set. The function body contains just a single TSQL statement, which results to a record-set and is returned from here.

-- Example:
--// Create Inline table-valued UDF [dbo].[ufn_itv_GetContactSales]
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[ufn_itv_GetContactSales](@ContactID int)
RETURNS TABLE
AS
RETURN (
	SELECT h.[ContactID], h.[SalesOrderID], p.[ProductID], p.[Name], h.[OrderDate], h.[DueDate],
	h.[ShipDate], h.[TotalDue], h.[Status], h.[SalesPersonID]
	FROM Sales.SalesOrderHeader AS h
	JOIN Sales.SalesOrderDetail AS d ON d.SalesOrderID = h.SalesOrderID
	JOIN Production.Product AS p ON p.ProductID = d.ProductID
	WHERE ContactID = @ContactID )

--// Usage:
SELECT * FROM ufn_itv_GetContactSales(100)

3. Multistatement table-valued function: Also returns a table (record-set) but can contain multiple TSQL statements or scripts and is defined in BEGIN END block. The final set of rows are then returned from here.

-- Example:
--// Create Multistatement table-valued UDF [dbo].[ufn_mtv_GetContactSales]
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[ufn_mtv_GetContactSales](@ContactID int)
RETURNS @retSalesInfo TABLE (
	[ContactID] INT NOT NULL,
	[SalesOrderID] INT NULL,
	[ProductID] INT NULL,
	[Name] NVARCHAR(50) NULL,
	[OrderDate] DATETIME NULL,
	[DueDate] DATETIME NULL,
	[ShipDate] DATETIME NULL,
	[TotalDue] MONEY NULL,
	[Status] TINYINT NULL,
	[SalesPersonID] INT NULL)
AS
BEGIN
	IF @ContactID IS NOT NULL
	BEGIN
		INSERT @retSalesInfo
		SELECT h.[ContactID], h.[SalesOrderID], p.[ProductID], p.[Name], h.[OrderDate], h.[DueDate],
			   h.[ShipDate], h.[TotalDue], h.[Status], h.[SalesPersonID]
		FROM Sales.SalesOrderHeader AS h
		JOIN Sales.SalesOrderDetail AS d ON d.SalesOrderID = h.SalesOrderID
		JOIN Production.Product AS p ON p.ProductID = d.ProductID
		WHERE ContactID = @ContactID
	END
	-- Return the recordsets
	RETURN
END

--// Usage:
SELECT * FROM ufn_mtv_GetContactSales(100)

– Output:

TVF & MVF output

More MSDN & MS BOL links:
http://msdn.microsoft.com/en-us/library/aa175085(SQL.80).aspx
http://msdn.microsoft.com/en-us/library/aa214363(SQL.80).aspx
http://msdn.microsoft.com/en-us/library/ms186755.aspx
http://msdn.microsoft.com/en-us/library/ms191007.aspx
http://msdn.microsoft.com/en-us/magazine/cc164062.aspx

OUTPUT clause and MERGE statement

Just responded to a post in MSDN forum, link: http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/c06e1db4-7fd6-43c4-8569-5335d555dac8

Accroding to MS-BOL, OUTPUT clause returns information from, or expressions based on, each row affected by an INSERT, UPDATE, DELETE, or MERGE statement. These results can be returned to the processing application for use in such things as confirmation messages, archiving, and other such application requirements. The results can also be inserted into a table or table variable. Additionally, you can capture the results of an OUTPUT clause in a nested INSERT, UPDATE, DELETE, or MERGE statement, and insert those results into a target table or view.

Lets go with a self descriptive example:

–> OUTPUT with INSERT

create table manoj (sn int, ename varchar(50))
insert into manoj
OUTPUT INSERTED.*
values (1,'manoj'), (2,'hema'), (3,'kanchan'), (4,'pankaj')

This gives me following output instead of normal message (N row(s) affected):
sn      ename
1	manoj
2	hema
3	kanchan
4	pankaj

select * from manoj

This gives me the same output as above:
sn      ename
1	manoj
2	hema
3	kanchan
4	pankaj

–> OUTPUT with DELETE

delete from manoj
OUTPUT DELETED.*
where sn = 4

This gives me following output:
sn      ename
4	pankaj

select * from manoj

Now the result set is changed to:
sn      ename
1	manoj
2	hema
3	kanchan

–> OUTPUT with UPDATE

update manoj
set ename = 'pankaj'
OUTPUT DELETED.*, INSERTED.*
from manoj
where sn = 2

This gives me following output:
sn      ename   sn     ename
2	hema	2	pankaj

select * from manoj

Now the result set is changed to:
sn      ename
1	manoj
2	pankaj
3	kanchan

–> OUTPUT with MERGE

According to MS-BOL, MERGE performs insert, update, or delete operations on a target table based on the results of a join with a source table. For example, you can synchronize two tables by inserting, updating, or deleting rows in one table based on differences found in the other table.

create table manoj2 (sn int, ename varchar(50))

insert into manoj2
values (1,'manoj'), (2,'hema'), (3,'kanchan'), (4,'pankaj'), (5,'saurabh')

select * from manoj2

This gives me following output instead of normal message (N row(s) affected):
sn      ename
1	manoj
2	hema
3	kanchan
4	pankaj

MERGE manoj AS TARGET
USING (SELECT sn, ename FROM manoj2) AS SOURCE
ON (TARGET.sn = SOURCE.sn)
WHEN MATCHED THEN
	UPDATE SET TARGET.ename = SOURCE.ename
WHEN NOT MATCHED BY TARGET THEN
	INSERT (sn, ename) VALUES (sn, ename)
OUTPUT $action, DELETED.*, INSERTED.*;

This gives me following output:
$action sn      ename   sn      ename
INSERT	NULL	NULL	4	pankaj
INSERT	NULL	NULL	5	saurabh
UPDATE	1	manoj	1	manoj
UPDATE	2	pankaj	2	hema
UPDATE	3	kanchan	3	kanchan

select * from manoj

Now the result set is changed to:
sn      ename
1	manoj
2	hema
3	kanchan
4	pankaj
5	saurabh

–> Final cleanup

drop table manoj
drop table manoj2

Plz note: An UPDATE, INSERT, or DELETE statement that has an OUTPUT clause will return rows to the client even if the statement encounters errors and is rolled back. The result should not be used if any error occurs when you run the statement.

MS BOL:-

- On MERGE: http://technet.microsoft.com/en-us/library/bb510625.aspx

- On OUTPUT: http://technet.microsoft.com/en-us/library/ms177564.aspx