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JSON In SQL Server

November 17, 2017 by robert

Finally in SQL Server 2016, Microsoft SQL Server now supports JSON serialization. It provides it through the FOR clause… like XML serialization. This will take a recordset and output it in JSON format with very little effort by the coder.

SELECT	AnimalID,
AnimalName,
Color
FROM	Animal
FOR	JSON PATH

As you can see. To get the output to come in JSON format, all you need to do is add FOR JSON PATH at the end of your query. Simple right? Here is what the results would look like.

[
	{
		"AnimalID":1,
		"AnimalName":"Dog",
		"Color":"Brown"
	},
	{
		"AnimalID":2,
		"AnimalName":"Flamingo",
		"Color":"Pink"
	},
	{
		"AnimalID":3,
		"AnimalName":"Polar Bear",
		"Color":"White"
	}
]

LIKE in SQL

July 8, 2016 by robert

The LIKE operator in SQL Server allows you to query data using patterns instead of exact matches. Normal select statements using the = operator will only return records where there is an exact match (usually the casing or trailing spaces do not matter). With the LIKE operator, it does not need to be an exact match.

LIKE
The most basic concept of the like operator is that it allows you to query data without using an exact match in the WHERE clause. It allows you to use some wildcard characters to get the results you are looking for. Here is a basic example:

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE 'Giant %'

The above statement uses the % as a wildcard. It basically says, show me any animals that start with the word Giant. This would return things like Giant Panda, Giant Squid, and Giant Clam.

Although % is the most common wildcard that is used with LIKE, there are many more. Here is a list of all the allowed wildcards.

%
Will allow zero or any characters. You can use this before, after, or in-between any string.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE 'GIANT %'
	OR AnimalName LIKE '% Penguin'
	OR AnimalName LIKE 'Hammer% Shark'

_
Will allow any 1 character.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE 'Chicke_'

[]
Will allow 1 character that is specified in the brackets. There are two ways to specify this. [a-d] or [abcd].

The following example will match both goose and moose.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE '[gm]oose'

The following example will match both cat and bat, but it will NOT match rat.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE '[a-d]at'

[^]
Will match any 1 character that is NOT specified in the brackets. There are two ways to specify this. [^a-d] or [^abcd].

The following example will match horse, but will NOT match zorse… and yes, zorse is an animal… I found it on the internet.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE '[^z]orse'

The following example will match rat, but will NOT match bat or cat.

SELECT	*
FROM	Animal
WHERE	AnimalName LIKE '[^a-d]at'

Important
If you are comparing a CHAR data type with the like operator, it may not work correctly. This because when you save data to a CHAR field it will space pad the field to the size of the field. To get around this, you need to trim the spaces from the end of the field.

SELECT	*
FROM	Animal
WHERE	RTRIM(AnimalName) LIKE '%monkey'

NOT Like
If you want to match where a pattern is NOT like a string, simply put the word NOT in front of the word LIKE.

SELECT	*
FROM	Animal
WHERE	AnimalName NOT LIKE ‘%monkey’

Escaping The Wildcard
From time to time you will need to actually search for a pattern containing one of the wildcard characters. Let’s say that you wanted to search for anything in a string that had 10% in it. The % (percent symbol) is a reserved word with the LIKE operator. You would search for the % character by using the ESCAPE clause.

SELECT	*
FROM	Invoice
WHERE	LineItemDescription LIKE '10!%%' ESCAPE '!'

In the query above, you can see that !% in the comparison string means to the literal character %. The ESCAPE clause tells the query to not apply the wildcard rules to any character following the specified characters. In this case, we are specifying the ! (exclamation mark).

Reference: https://msdn.microsoft.com/en-us/library/ms179859.aspx

How To Use The OUTPUT Clause

November 5, 2014 by robert

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

Case Sensitive Compare

November 4, 2014October 3, 2014 by robert

Occasionally we need to do a string comparison in SQL Server as a case sensitive compare. By default, case sensitive compare is not turned on for tables in SQL Server. It’s actually pretty easy to change a string comparison to a case sensitive compare. You can do this by using the COLLATE clause.

Read below to find out why this works and other tips on doing a case sensitive compare.

SELECT	A.AnimalID, A.AnimalName, AFT.FeedingTime
FROM	Animal A
INNER	JOIN AnimalFeedingTime AFT ON AFT.AnimalName = A.AnimalName COLLATE SQL_Latin1_General_CP1_CS_AS

What Is The COLLATE Clause

The COLLATE clause is something that you can add to the end of an expression to set the collation of the operation to a specific collation. So in the example… the string equal comparison is being changed to a collation of SQL_Latin1_General_CP1_CS_AS.

A collation in SQL Server is something defines how data is compared. This could be things like case sensitivity, acceptable characters, etc… Most of the time (for English installations of SQL Server) it will be a collation type of SQL_Latin1_General_CP1_CI_AS. This is because the Latin character set covers English and other Latin based languages.

The two most common collations that I deal with are SQL_Latin1_General_CP1_CI_AS and SQL_Latin1_General_CP1_CS_AS. You can see that they are very similar. In fact… the only difference is the _CI_ and _CS_. These actually stand for Case-Insensitive and Case-Sensitive.

Field Level Case Sensitivity

Even better… you don’t need to set the collation on every sql statement that you want to make case sensitive. There is actually a setting that you can apply to a field in a table.

NOTE: that if you are joining on this table, both collations must be the same or you will need to specify the collation to use.

Create a new table with a case sensitive field

CREATE
TABLE	Animal
(AnimalID		INT,
AnimalName	VARCHAR(100) COLLATE SQL_Latin1_General_CP1_CS_AS)

Change a table’s column to be case sensitive

ALTER
TABLE	Animals
ALTER	COLUMN AnimalName VARCHAR(100) COLLATE SQL_Latin1_General_CP1_CS_AS