robert

How To Use The OUTPUT Clause

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The OUTPUT clause is an amazing part of SQL Server that many people do not know about.  As corny as it is, I still remember the day that I found it.  I had been searching for the whole day trying to figure out how to get the identity values from a large amount of data that I just inserted in to the database.  There had to be a way… right?  After searching and searching, I gave up and just accepted that it is not possible… a few days later I found exactly what I was looking for… the OUTPUT clause.

 
The OUTPUT clause is a part of the query that will return data from before or after the operations is completed.  Let’s say that you inserted data in to a table and you wanted the ID column values (which are auto-numbers).  The OUTPUT clause gives you this information!  It can work on INSERT, DELETE, UPDATE, and MERGE statements.  I will take you through examples of each.

 
To access the data that is being altered in your sql statement, you need to use special column prefixes that SQL Server makes available to you.  The two special prefixes are “inserted” and “deleted”.  During an insert statement, the inserted prefix is available for you to use.  During a delete statement, the deleted prefix is available to you.  During the update and merge statements, both the deleted and inserted prefixes are available to you.  In these cases, the deleted represents the data before it was changed and the inserted represents the data after it was changed.

 
One thing to note is that the data being outputted must go in to a table or table variable.

 
OUTPUT Clause On An INSERT Statement

DECLARE	@OutputData	TABLE
		(AnimalID	INT,
		 AnimalName	VARCHAR(50))

-- Insert into the table and stick the resulting animal
--   name and identity column in to a temp variable
INSERT
INTO	Animal
		(AnimalName)
OUTPUT	inserted.AnimalID, inserted.AnimalName
INTO	@OutputData
		(AnimalID, AnimalName)
VALUES	('Pig'),
		('Dog'),
		('Chinchilla')

-- View the inserted data
SELECT	*
FROM	@OutputData

 
OUTPUT Clause On A DELETE Statement

DECLARE	@OutputData	TABLE
		(AnimalID	INT,
		 AnimalName	VARCHAR(50))

DELETE
FROM	Animal
OUTPUT	deleted.AnimalID, deleted.AnimalName
INTO	@OutputData
		(AnimalID, AnimalName)
WHERE	AnimalName = 'Pig'

-- View the deleted data
SELECT	*
FROM	@OutputData

 
OUTPUT Clause On An UPDATE Statement 

DECLARE	@OutputData	TABLE
		(AnimalID	INT,
		 OldAnimalName	VARCHAR(50) ,
		 NewAnimalName	VARCHAR(50))

-- Update the table and output the animal name
--   and identity column to the temp table
UPDATE	Animal
SET	AnimalName = 'Swine'
OUTPUT	inserted.AnimalID, deleted.AnimalName, inserted.AnimalName
INTO	@OutputData
		(AnimalID, OldAnimalName, NewAnimalName)
WHERE	AnimalName = 'Pig'

-- View the updated data
SELECT	*
FROM	@OutputData

 
OUTPUT Clause On A MERGE Statement

DECLARE	@OutputData	TABLE
		(AnimalID	INT,
		 OldAnimalName	VARCHAR(50),
		 NewAnimalName	VARCHAR(50))

DECLARE	@ChangeData	TABLE
		(OldAnimalName	VARCHAR(50),
		 NewAnimalName	VARCHAR(50))

INSERT
INTO	@ChangeData
VALUES	('Pig', 'Swine')

-- Update the table and output the animal name
--   and identity column to the temp table
MERGE	Animal AS target
USING	@ChangeData AS source
		ON (source.OldAnimalName = target.AnimalName)
WHEN	MATCHED
THEN	UPDATE
		SET target.AnimalName = source.NewAnimalName
OUTPUT	inserted.AnimalID, deleted.AnimalName, inserted.AnimalName
INTO	@OutputData
		(AnimalID, OldAnimalName, NewAnimalName);

-- View the updated data
SELECT	*
FROM	@OutputData

 
 
Reference: http://msdn.microsoft.com/en-us/library/ms177564.aspx

 

Order By On A Union?

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Have you ever tried to add an ORDER BY clause to a UNION operator and have gotten this error message?

Msg 156, Level 15, State 1, Line 4
Incorrect syntax near the keyword ‘UNION’.

SELECT	AnimalName
FROM	Animal
ORDER	BY AnimalName

UNION

SELECT	AnimalName
FROM	Animal
ORDER	BY AnimalName

So what the heck is this and how do we fix it?

 
What The Error Says
The error basically says that you have an issue with your syntax. The ORDER BY clause should only be applied one time in your query. Logically SQL Server will pull the data requested from the two tables… then it will perform the sort operation on the data.

When people see the UNION operator, they think that it is combining two different result sets, thus they need two ORDER BY clauses. In fact, you only need to order the final result set. This is done by placing the ORDER BY command at the very end of the statement.

SELECT AnimalName
FROM Animal
-- Notice the removed ORDER BY here?

UNION

SELECT AnimalName
FROM Animal
ORDER BY AnimalName

 

List Of Data Types And Their Sizes

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The below table shows the storage sizes of the different data types in SQL Server.

[table caption=”DateTime Data Types” th=”0″ width=”500″ colwidth=”150|150″]
date,3 bytes
datetime,8 bytes
datetime2,6 – 8 bytes (depending on precision)
datetimeoffset,10 bytes
smalldatetime,4 bytes
time,5 bytes
[/table]

[table caption=”Numeric Data Types” th=”0″ width=”500″ colwidth=”150|150″]
decimal,5 – 17 bytes
numeric,5 – 17 bytes
float,4 or 8 bytes
real,4 bytes
bigint,8 bytes
int,4 bytes
smallint,2 bytes
tinyint,1 byte
money,8 bytes
smallmoney,4 bytes
[/table]

[table caption=”String” th=”0″ width=”500″ colwidth=”150|150″]
char,size defined in table
varchar,2 bytes + data size
text,data size
nchar,2 times size defined in table
nvarchar,2 bytes + 2 times data size
ntext,2 times data size
[/table]

[table caption=”Binary” th=”0″ width=”500″ colwidth=”150|150″]
binary,size defined in table
varbinary,2 bytes + data size
image,2 bytes + data size
[/table]

[table caption=”Other” th=”0″ width=”500″ colwidth=”150|150″]
bit,1 byte
hierarchyid,5 bytes
uniqueidentifier,16 bytes
[/table]

Reference: http://msdn.microsoft.com/en-us/library/ff848794.aspx

Parse XML With SQL Server

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SQL Server has a lot of useful functionality built-in when it comes to XML.  Today I want to show you an easy way to parse XML data in to a usable format inside your query.

 
For this example, I will be parsing XML data into a temp table, then inserting that data in to a table.

DECLARE	@XMLToParse  XML

-- Load the XML data in to a variable to work with.
-- This would typically be passed as a parameter to a stored proc
SET	@XMLToParse =	'<Animals>
			   <LandAnimals>
				<Animal>Baboon</Animal>
				<Animal>Yak</Animal>
				<Animal>Zebra</Animal>
			   </LandAnimals>
			</Animals>'

-- Declare temp table to parse data into
DECLARE	@ParsingTable  TABLE
	(Animal	VARCHAR(100))

-- Parse the XML in to the temp table declared above
INSERT
INTO	@ParsingTable
	(Animal)
SELECT	xmlData.A.value('.', 'VARCHAR(100)') AS Animal
FROM	@XMLToParse.nodes('Animals/LandAnimals/Animal') xmlData(A)

-- Insert into the actual table from the temp table

INSERT
INTO	Animals
	(AnimalName)
SELECT	Animal
FROM	@ParsingTable

 
The statement that parses the XML has 2 parts to it.

FROM   @XMLToParse.nodes('Animals/LandAnimals/Animal') xmlData(A)

This part says to parse the @XMLToParse variable (previously filled with the XML file) using the method built in to SQL Server called .nodes.  It specifies the repeating node to be Animals/LandAnimals/Animal.  It assigns an aliases this XML parsed records as a table named xmlData.  The (A) is the column name of the rowset.  This will be referenced in the select part of the statement.

 

SELECT  xmlData.A.value('.', 'VARCHAR(100)') AS Animal

The select part of this statement references xmlData (which is the table aliases) and A (which is the column named for that table).  It calls the .value function to return the value from the table/column.  For the .value function, you pass in 2 elements.

The first element is the field.  In this case we are passing in just a period.  We do this because there is no node below the Animal node.  If there was, we would need to specify it here..

The second parameter is the datatype that you would like the value to be casted as.  Then I always aliases the field to something relevant.

 
Although parsing XML can be a little confusing in SQL Server, it is very powerful.  This is a great way to pass bulk data to a stored procedure from any type of client application.

SQL Server Management Studio Keyboard Shortcuts

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Although some of these keyboard shortcuts may seem a little odd at first… once you start using them I think that you’ll love them and use them all the time.

Ctrl + R – Show/Hide the results pane

Ctrl + N – New query window

Ctrl + Shift + U – Switch current selection to uppercase

Ctrl + Shift + L – Switch current selection to lowercase

F5 – Execute the currently selected query (or entire query if nothing is selected)

Ctrl + Tab – Switch to the next open tab

Ctrl + Shift + Tab – Switch to the previous open tab

Ctrl + Space – Pops up IntelliSense complete if it is not already open

Ctrl + Shift + R – Refresh local IntelliSense cache

F8 – Open the Object Explorer if not already open

 

 What other SSMS keyboard shortcuts do you use?