tables

Parsing A Delimited String In SQL Server

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At some point in your life, you’ve probably had to parse a string inside SQL Server. Maybe you had a comma delimited string and you need the data inside a table. So, you go to stackoverflow and find some stored procedure that someone made that you don’t understand. It works, but yuck. Well… those days are over! In SQL 20016 they introduced a new table-valued function called STRING_SPLIT. This makes is very easy to parse a comma delimited string in SQL Server.

 
STRING_SPLIT Basics
The STRING_SPLIT function is really easy to use. It basically just takes 2 parameters. The first parameter is the string that you want to parse. The second parameter is the delimiter for parsing on.

The STRING_SPLIT function will always return a one column result set with a column named value.

Here’s an example of how to use it:

SELECT	value AS AnimalName
FROM	STRING_SPLIT('Dog,Cat,Bird,Walrus', ',')

[table width=”150″ colwidth=”150″ colalign=”left”]
value
Dog
Cat
Bird
Walrus
[/table]

 
If your input string has spaces by the delimiter, you just need to trim the value that you get from the function. Here’s an example of trimming the spaces and also parsing on a pipe character:

SELECT	value AS AnimalName
FROM	STRING_SPLIT('Dog |Cat |Bird | Walrus', '|')

 
 
Source: https://docs.microsoft.com/en-us/sql/t-sql/functions/string-split-transact-sql

Cross Apply In SQL

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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 simplify 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.

SELECT	A.AnimalName,
		H.HabitatName
FROM	Animal A
CROSS	APPLY GetAnimalHabitat(A.AnimalTypeCode) H

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

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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.

SELECT	TOP 1
		InvoiceFile.PathName() AS DirectoryOfFile
FROM	Invoice

SQL Server Rename Column

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This article will cover how to rename a column in SQL Server. The function of a SQL Server rename column is not performed too often. Usually we do this when we roll out a new product and we want to make a column more generic.

 
SQL Server Rename Column (SQL Server 2005 and beyond)

They make this super simple. Just remember to put to single quotes around the parameters.

EXEC	sp_rename 'Animals.AnimalName', 'AnimalRealName', 'COLUMN'

The above SQL Server rename column code snippet has a few parts to it. Here is the breakdown:

  • sp_rename – This is a system stored procedure will rename different types of objects in SQL Server.
  • ‘Animals.AnimalName’ – This is the tablename and column that I would like to rename.
  • ‘AnimalRealName’ – This is the new name that I would like to call the column.
  • ‘COLUMN’ – This is the type of object that you would like to rename is. To rename a column, always leave this value ‘COLUMN’.

 
If you would like to know how to do a SQL Server rename column for SQL Server versions prior to 2005, please leave a note in the comments.

 
 
Reference: http://msdn.microsoft.com/en-us/library/ms188351(v=sql.90).aspx

SQL Server 2014 Feature – Non-Clustered Indexes For Table Variables

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This is truly an amazing feature to add to SQL Server 2014. I use table variables all the time and this was the only thing I didn’t like about them. Up to this point, SQL Server did not support having non-clustered indexes on table variables (the one with the name that starts with the @). If you wanted to do this, you had to create/use a temp table (the one with the name that starts with #).

With SQL Server 2014, they changed this and now allow the table variables to have non-clustered indexes as well. To do this, we simply add a little bit of extra code after the column declaration.

DECLARE	@AnimalTableVar	TABLE
( AnimalID		INT,
  AnimalName	VARCHAR(50)	INDEX IX_AnimalTempTable_AnimalName
)

In the sample above, we create a table variable called @AnimalTableVar. Then when we declare the column AnimalName, we add an index called IX_AnimalTempTable_AnimalName.

Here is how selecting from this table shows up in the execution plan!
Non-Clustered Indexes For Table Variables

Reference: http://msdn.microsoft.com/en-us/library/ms188927(v=sql.120).aspx