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.

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:

AnimalID AnimalName AnimalType Animal Weight
35 Giant Squid Fish 400
36 Giant Panda Mammal 500
37 Giant Clam Fish 60

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.

AnimalID AnimalName AnimalType Animal Weight
35 Giant Squid Fish 400
36 Giant Panda Mammal 500
37 Giant Clam Fish 60
38 Emperor Penguin Bird 15
39 Hammer Head Shark Fish 90

Will allow any 1 character.

AnimalID AnimalName AnimalType Animal Weight
18 Chicken Bird 5

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.

AnimalID AnimalName AnimalType Animal Weight
11 Goose Bird 15
27 Moose Mammal 1000

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

AnimalID AnimalName AnimalType Animal Weight
10 Cat Mammal 10
34 Bat Bird 1

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.

AnimalID AnimalName AnimalType Animal Weight
6 Horse Mammal 750

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

AnimalID AnimalName AnimalType Animal Weight
33 Rat Mammal 1

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.

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.

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.

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).

InvoiceID ItemName LineItemDescription
1 Coupon Code 10% off web coupon


How To Pull Single Value From XML


SQL Server has a built in method for easily pulling one value from an XML. To do this you use the method called .value(). The .value method will run an XQuery against the XML specified in the query. This method is scalar, so it will only return 1 value. You cannot use this to return multiple values.

In the query above, you can see that you can just pass the xpath and the datatype that you want the output to be. This will pull that value out of the XML and put it in the specified format. You can see that after the xpath, there is a funny syntax [1]. This tells SQL Server to grab the first instance of the AnimalName node. You need to do this because the .value() method only returns one value and will not work with a repeating node.


Cross Apply In SQL


CROSS APPLY is one of those helpful things in SQL Server that most people don’t think of or may not even know about. In this article I’d like to talk about what the APPLY operator is and how we can use it to simply our sql statements.

APPLY Operator
The APPLY operator allows you to join a table to a table-valued function. A table-valued function is a function that will return a table with one or more columns. With the apply operator, you can pass values from the first table in to the table-valued function.

There are only 2 types of APPLY operators:
CROSS APPLY – Returns records when a value from both sides of the operator match. Like an INNER JOIN.
OUTER APPLY – Returns all rows from the other side of the operator and will return the value or NULL from the table-valued function. This is like an OUTER JOIN.

In the example above, you can see that we join to the GetAnimalHabitat function using the CROSS APPLY. You can imagine that this function does a bunch of logic that is not visible in this query. If the GetAnimalHabitat function had 25 lines of code, you can see how this simplifies the above query dramatically.

Additional Thoughts
The APPLY operator can simplify the code, but could be accomplished by joining to a sub query as well. One difference is that the function in the APPLY operator is being executed for every row in the outer table. If you use the APPLY operator, make sure that you test the speed of your query to make sure that it did not degrade performance.

Get Filestream Storage Directory


Filestreams are a great way to store files in SQL Server. SQL Server makes this super easy by managing the storage of the physical files on the file system somewhere. But what if you want to get access to these files or if you just want to know where they’re stored. SQL Server provides a function called PathName that you can call to get this path. You call this function like you would call an extension method in .Net. In the example below, we’ll assume that the column InvoiceFile is a Filestream datatype.

Estimate Backup Size In Sql Server


When you’re creating your database backup maintenance plans, you need to choose a drive that has enough space for your backup. So how much space will you actually need to backup your database? Figuring this out is actually a lot easier than you would expect.

Although it won’t be 100% accurate, SQL Server has a built in stored procedure that will get you pretty close. You can use the sp_spaceused stored procedure to show you the amount of space used in your database. Now keep in mind that a full database backup only stores the actual data/objects in the database. The unused space is not stored in the backup.

Estimate Backup Size In SQL Server

In the example above we call the sp_spaceused stored procedure from the database that we want to get the backup size for. This stored procedure will return a couple datasets with multiple columns. The column that you will look at is named reserved. This will show you a good estimate of how large your full backup file will be.

More Info
The @updateusage parameter, in the example above, tells the stored procedure to update the space usage statistics before returning the database size information. Passing TRUE in to this parameter will give us the most accurate size estimate.