SQL Server REVERSE String Function with Examples 2008, R2, 2012, 2014

The SQL Server REVERSE string function can be quite useful if you need to return a string or sequence in reverse order.  It can also be quite powerful when used in combination of other SQL keywords (CHARINDEX, RIGHT).  We’ll start by looking at some of the simple uses.

[Sarcasm to follow]

So say you’re and android and you’ve always dreamed of reversing your name and have gone your whole life up to this point just waiting to be able to do it in SQL.  Today is your lucky day!  The code below will magically turn your name into its REVERSE version.

SELECT REVERSE('COMMANDER DATA');
--------------
ATAD REDNAMMOC

(1 row(s) affected)

Fantastic.  This could also assist you if  you’re anticipating getting pulled over by the cops for a sobriety test and can’t quite remember how to say the alphabet backwards.

REVERSE can also flip number sequences!  This works, of course, because SQL Server converts the numbers to a varchar first.

SELECT REVERSE(1234567890);
------------
0987654321

(1 row(s) affected)

Ok. Ok.  Not impressed I see.  Then perhaps you’re a word nerd and are big into palindromes.  We can use the SQL Server REVERSE function to help us determine if a word is a palindrome like so…

DECLARE @palindromeTest VARCHAR(100) = 'RACECAR';
IF(@palindromeTest = REVERSE(@palindromeTest))
	SELECT 'THIS IS A PALINDROME!';
ELSE
	SELECT 'THIS IS NOT A PALINDROME';
--------------------
THIS IS A PALINDROME

(1 row(s) affected)

Note that in SQL Server 2008+ you can declare and set a variable in one line.

Still not impressed.  Maybe you are a serious nerd and are into DNA sequencing.  Often times you’ll need to find the reverse, complement, or reverse-complement of a DNA sequence.  While REVERSE won’t help you with the complement portion of the problem, it will certainly help you reverse your sequence.

-- REVERSE A DNA SEQUENCE
DECLARE @dnaSequence VARCHAR(100) = 'GGGatttataaaaaata';
SELECT REVERSE(@dnaSequence);
-----------------
ataaaaaatatttaGGG

(1 row(s) affected)

Pretty amazing stuff.

Now, going for broke, I’ll be providing a few more complex examples of REVERSE and a useful UDF (user defined function) to make things a bit more convenient.

The last couple of scenarios I want to cover is when you need to pull a filename off the end of a URL and full or absolute path.  The technique is identical for all cases as shown below.  I incorporated both examples into one to show the similarities.

-- GET THE FILENAME FROM URL
-- GET THE FILENAME FROM A FULL PATH
DECLARE @URL VARCHAR(1000);
DECLARE @FULLPATH VARCHAR(1000)
DECLARE @URLFILENAME VARCHAR(100);
DECLARE @FULLPATHFILENAME VARCHAR(100);

SET @URL = 'HTTP://EXAMPLESQL.COM/SQL-RESOURCES/RESOURCE.PHP';
SET @FULLPATH = '/HOME/FTP/CLIENTS/ACME/TEST.TXT';

-- THESE ARE EXACTLY THE SAME!
-- YOU MIGHT MAKE A USER DEFINED FUNCTION (UDF) TO DO THIS IF YOU PLAN ON USING IT A BUNCH
-- BUT BE AWARE THAT A CALL TO A UDF DOES CAUSE A PERFORMANCE DECREASE
SET @URLFILENAME = RIGHT(@URL, CHARINDEX('/', REVERSE(@URL))-1);
SET @FULLPATHFILENAME = RIGHT(@FULLPATH, CHARINDEX('/', REVERSE(@FULLPATH))-1);

SELECT @URLFILENAME;
SELECT @FULLPATHFILENAME;

GO
------------
RESOURCE.PHP

(1 row(s) affected)

---------
TEST.TXT

(1 row(s) affected)

Lastly, I wanted to show everyone a helpful UDF that will essentially encapsulate the magic above into a single callable function.

IF EXISTS(SELECT 1 FROM sys.sysobjects WHERE id = OBJECT_ID(N'udfGetFilenameFromPathOrUrl') AND xtype IN (N'FN', N'IF', N'TF'))
	DROP FUNCTION udfGetFilenameFromPathOrUrl;
GO

CREATE FUNCTION udfGetFilenameFromPathOrUrl(
	@PATHVAR VARCHAR(1000),
	@DELIMITER CHAR(1)	
)
RETURNS VARCHAR(200)
BEGIN
	RETURN RIGHT(@PATHVAR, CHARINDEX(@DELIMITER, REVERSE(@PATHVAR))-1);;
END
GO

And using the function…

DECLARE @URL VARCHAR(1000) = 'HTTP://EXAMPLESQL.COM/SQL-RESOURCES/RESOURCE.PHP';
SELECT dbo.udfGetFilenameFromPathOrUrl(@URL, '/');
-------------
RESOURCE.PHP

(1 row(s) affected)

So there you have it.  The SQL Server REVERSE function can be useful as we can see from the examples above.  Be careful how you wield this power though.  😉

Valid for SQL Server  2008, 2008 R2, 2012, 2014.

DECLARE and SET Variables in one line SQL Server 2008, R2, 2012, 2014

How many times do we as SQL developers have to declare and set variables?  I recon that this occurs quite frequently, perhaps a million times a day…well, maybe not that many but it FEELS like it sometimes.  Prior to SQL Server 2008, we were forced to declare the variable in one statement and then set it in a following statement.  We got used to it but it was a constant annoyance for those of us to have better things to do then fiddle with SET statements every other line.

With SQL Server 2008, 2012 and above, we can now declare and set variables in a single statement.

-- Old clunky way of doing things prior to SQL Server 2008
DECLARE @myVar VARCHAR(100);
SET @myVar = 'Some Value';

-- New, amazing way of declaring variables
DECLARE @myVar VARCHAR(100) = 'Some Value';

We can see above the old, nasty way we are all familiar with.  Then we see the amazingly simple and efficient way we can do it now with SQL Server 2008 and above.  I bet we save on average of 10-12 keystrokes.  Multiplying that times the million times we have to do this a day and you’ll see we end up with quite a significant savings of work.  Your life just got a bit better!

Power on SQL Devs!

Here is the full technical reference for declaring a setting variables in SQL Server 2014.

Valid for SQL Server 2008, 2008 R2, 2012, 2014.

SQL Server 2012 Date and Time Functions

Hi All.  I’ve put together an alphabetical reference list for SQL Server 2012 Date and Time Functions which may come in handy when you’ve forgotten a particular keyword or just want to see what is available in one place without referencing books online.  There are 26 items in the list.

@@DATEFIRST
CURRENT_TIMESTAMP
DATEADD
DATEDIFF
DATEFROMPARTS
DATENAME
DATEPART
DATETIME2FROMPARTS
DATETIMEFROMPARTS
DATETIMEOFFSETFROMPARTS
DAY
EOMONTH
GETDATE
GETUTCDATE
ISDATE
MONTH
SET DATEFIRST
SET DATEFORMAT
SMALLDATETIMEFROMPARTS
SWITCHOFFSET
SYSDATETIME
SYSDATETIMEOFFSET
SYSUTCDATETIME
TIMEFROMPARTS
TODATETIMEOFFSET
YEAR

SQL Server 2012 String Functions List

Hi Everyone.  In this post I’m simply listing off all SQL Server 2012 string functions alphabetically for quick reference.  In all, there are 25 keywords in the list.

SQL Server 2012 String Functions

ASCII
CHAR
CHARINDEX
CONCAT
DIFFERENCE
FORMAT
LEFT
LEN
LOWER
LTRIM
NCHAR
PATINDEX
QUOTENAME
REPLACE
REPLICATE
REVERSE
RIGHT
RTRIM
SOUNDEX
SPACE
STR
STUFF
SUBSTRING
UNICODE
UPPER

How to send a variable to a sql script from a batch file or command line with sqlcmd -v 2008, R2, 2012, 2014

Topic: sqlcmd variable from a batch file to a sql script

Scripting is a powerful way to automate your systems.  It should come as no surprise to discover that SQL Server provides a way for developers to send in parameters to a sql script using a batch file via the sqlcmd utility (for SQL Server 2005 and later).  sqlcmd is a very versitile utility and I’ll be covering more of its uses in other posts but we’re focusing on sending a variable (possibly more than one) to a sql script either in a batch file or straight from the command line.  So without further ado, let’s take a quick look at the syntax…

sqlcmd -v <name of variable>=<value> -v <name of variable>=<value>

This first example is showing the basic idea around passing multiple variables in on the command line using the -v switch followed by the variable name equals value. To be practical, you might need to use a few other switches in order to tell sqlcmd the server you want to connect to ‘-S’ followed by the user (-U) and password (-P). The ‘-S’ is required for SQL Express and the ‘-U’ and ‘-P’ might be required if you’re using SQL Server authentication.  Last but not least is the ‘-i’ which tells sqlcmd  that there are input file(s) to follow.  Yes, you can have more than one of these as well and if you list more than one file they’ll be executed in order.

sqlcmd -S <sql server instance name> -U <username> -P <password> -v <name of variable>=<value> -i <your script.sql>[,file2...]

To really bring this home to roost we also need to know how to access the variable once it has been passed in to our sql script.  This is done by using the following…

$(variable)

So, now we’ve defined all the essentials let’s put it all together to make something that actually works.

First, we’ll create an extremely simple sql script named script.sql and place this code in it…

SELECT $(path);

Next, lets create a file named batchfile.bat and place the following inside of it…

sqlcmd -S EXAMPLESQL-COM-PC\SQLEXPRESS -v path="'C:\test\test'" -i script.sql,script.sql

From the command line (assuming both files are in the same place) we execute the batch file…

------------
C:\test\test
(1 rows affected)
------------
C:\test\test
(1 rows affected)

A couple of final notes.  I passed the same script file in twice just to show you what that look like.  There shouldn’t be any spaces between the files.  Also, the dealing with paths specifically, you’ll need to make sure you quote them properly like I did above or else they won’t work properly.  You’ll need to change the -S string to your sql server instance name if you want to give this a try.

Valid for SQL Server 2005, 2008, R2, 2012, 2014.

Happy coding!

How to use the SQL Server RIGHT string function with T-SQL Examples 2005, 2008, R2, 2012, 2014

The SQL Server RIGHT string function gives us the ability to return a given number of characters from a string on its rightmost side.  For example, say we have the text ‘Bill Jones’.  We can use the RIGHT function to return ‘Jones’ without having to parse the string from the beginning.  Let’s look at some code…

RIGHT ( string , int )

The code above is the syntax of the RIGHT function.  The first parameter is a string and the second is an integer letting sql server know how many rightmost characters you want from the string in the first parameter.  Let’s go back to our initial example from above…

SELECT RIGHT ('Bill Jones', 5);

The result of this query are:

Jones

Pretty simple stuff.  To use the SQL Server RIGHT function in a more practical way we might use it with a table.  So, let’s define a table called Document and fill it with some sample filenames.  We’ll then use the RIGHT and LEFT functions to help us fill in the extension for each file.

-- create the document table
CREATE TABLE Document (
Filename VARCHAR(50),
Extension VARCHAR(10)
);

-- insert the demo rows into the document table
INSERT INTO Document ([Filename]) VALUES ('family.jpg');
INSERT INTO Document ([Filename]) VALUES ('lessons.docx');
INSERT INTO Document ([Filename]) VALUES ('schemas.xml');
INSERT INTO Document ([Filename]) VALUES ('report.ps');
INSERT INTO Document ([Filename]) VALUES ('puppies.report');
INSERT INTO Document ([Filename]) VALUES ('secret.password');

-- get extension column size - this is a bit advanced since 
-- we are looking at the table's meta data to set our max
-- column size.  the query below works whenever you don't 
-- know the column size ahead of time and need to find it
-- dynamically.  
DECLARE @extensionColumnSize INT;
SELECT @extensionColumnSize = character_maximum_length    
    FROM information_schema.columns  
    WHERE TABLE_NAME = 'Document' AND COLUMN_NAME = 'Extension';

-- get the extension for each filename
DECLARE @i INT;
SET @i = 1;
WHILE @i < @extensionColumnSize
BEGIN
   UPDATE Document
   SET [Extension] = RIGHT([Filename], @i-1) FROM Document a
   WHERE (LEFT(RIGHT([Filename], @i),1)) = '.';

   SET @i = @i + 1;
END

-- table extensions should be filled in now
SELECT * FROM Document;

-- clean up by dropping/deleting table
DROP TABLE Document;

The first part of the example simply creates the Document table and fills it with six rows of data.  The second part is the juicy stuff.  First we find the maximum possible length of  an extension by getting the size of the Extension column from the database meta data.  Next, we loop from 1 to Extension column size which, in this case, is 10.  Each time through the loop we get the rightmost @i letters and check to see if a period is on the leftmost part of the string.  If it is a period then we update the Extension column with the rightmost @-1 characters (we don’t save the period).

I’ll admit that the example is not very simple.  However, you could ‘simplify’ the code above  as above but replacing lines 15-35 with the following…

UPDATE Document SET [Extension] = RIGHT([Filename], CHARINDEX('.', REVERSE([Filename]))-1);

It’s actually quite funny how much less code it takes.  The good thing with that one liner is that we don’t have to loop and deal with all kinds of variables and system tables but we do have to know about CHARINDEX and REVERSE…two more sql server functions.  I’ll be discussing those in later posts.  I think the first example, while perhaps a bit contrived, does provide some code that you might be able to repurpose for your own uses.  I cheated a little as well by also using the SQL Server LEFT function but you’ll find that they can be used together quite powerfully.

The results of the running code (either method) are below.

Filename                                           Extension
-------------------------------------------------- ----------
family.jpg                                         jpg
lessons.docx                                       docx
schemas.xml                                        xml
report.ps                                          ps
puppies.report                                     report
secret.password                                    password

So thats the SQL Server Right function and hopefully the example above will give you some ideas of your own on how to use it.

Valid for SQL Server 2005, 2008, R2, 2012, 2014

Happy coding!

 

How to use MySQL exit and quit and \q commands with examples

In this post I’m going to quickly explain how to use MySQL exit and quit and \q commands to return to the operating system’s command line shell.

When working with MySQL at the command line you’ll arrive at a point when you are finished working.  Thus, you’ll want to exit mysql and return back to your operating system’s command shell.  MySQL provides two keywords for doing this, namely, exit and quit as well as a shorthand version \q.

So for example, say you’re sitting at the mysql command line and it looks like this…

mysql>

And you wish to go back to your command shell…

mysql>exit

-OR-

mysql>quit

(Type either exit or quit and press enter)

You can also use some shorthand to exit or quit the command line.  You can use the \q to quit as well.

It looks like this…

mysql>\q

(Type \q and press enter)

It’s as simple as that.  Learning how to use the MySQL command line can be powerful and efficient.  These three commands will help you on your way to using the command line more effectively.

 

Basic, Simple, Useful and Practical Examples of T-SQL SELECT 2005, 2008, R2, 2012, 2014

Topic: T-SQL SELECT (This article is about MS SQL Server)

If you haven’t installed SQL Server yet then you’ll need to get it here.

Data in your database is stored in a structure called a TABLE.  Tables have columns (hopefully with useful names).  On the surface, a table looks alot like an Excel spreadsheet and that can be a useful way to think about them when you’re just starting out.  The best way to learn about the SELECT command is by doing so let’s jump right into some examples.

Example

Let suppose we have a database called AdventureWorks2012 (an example database available from Microsoft for free here) and a table called Person.Person.  It looks like this

Person.Person Table Definition

Person.Person Table Definition

 

 

You can imagine the table looking something like this under the covers…

BusinessEntityID FirstName MiddleName LastName Suffix EmailPromotion Demographics rowguid ModifiedDate
1 Billy The Kid Jr. Business 18-25 92C4279F-1207-48A3-8448-4636514EB7E2 2013-08-16 00:00:00.000
2 Gertude J Miller NULL Consumer 65+ F2D7CE06-38B3-4357-805B-F4B6B71C01FF 2012-11-23 00:00:00.000

As you can see it has the following columns: BusinessEntityID, PersonType, NameStyle, Title, FirstName, MiddleName, LastName, Suffix, EmailPromotion, AdditionalContactInfo, Demographics, rowguid, ModifiedDate.  In the image, you’ll see after the column name is some additional information in parenthesis.  This extra information is describing the type of data that particular column can hold.  I won’t get into it in this post but basically it is good database design to ensure that your data is consistent.  Therefore, you only put numbers in columns that take numbers and you only put dates in columns that accept dates and so on and so forth.

The quickest and dirtiest way to get information from a table is to execute a SELECT query like this:

SELECT * FROM AdventureWorks2008.Person.Person

The asterisk (star) basically says to grab all columns from the table.

Results:

BusinessEntityID	PersonType	NameStyle	Title	FirstName	MiddleName	LastName	Suffix	EmailPromotion	AdditionalContactInfo	Demographics	rowguid	ModifiedDate
1	EM	0	NULL	Ken	J	Sánchez	NULL	0	NULL	<IndividualSurvey xmlns="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/IndividualSurvey"><TotalPurchaseYTD>0</TotalPurchaseYTD></IndividualSurvey>	92C4279F-1207-48A3-8448-4636514EB7E2	1999-02-08 00:00:00.000
2	EM	0	NULL	Terri	Lee	Duffy	NULL	1	NULL	<IndividualSurvey xmlns="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/IndividualSurvey"><TotalPurchaseYTD>0</TotalPurchaseYTD></IndividualSurvey>	D8763459-8AA8-47CC-AFF7-C9079AF79033	1998-02-24 00:00:00.000
3	EM	0	NULL	Roberto	NULL	Tamburello	NULL	0	NULL	<IndividualSurvey xmlns="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/IndividualSurvey"><TotalPurchaseYTD>0</TotalPurchaseYTD></IndividualSurvey>	E1A2555E-0828-434B-A33B-6F38136A37DE	1997-12-05 00:00:00.000
4	EM	0	NULL	Rob	NULL	Walters	NULL	0	NULL	<IndividualSurvey xmlns="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/IndividualSurvey"><TotalPurchaseYTD>0</TotalPurchaseYTD></IndividualSurvey>	F2D7CE06-38B3-4357-805B-F4B6B71C01FF	1997-12-29 00:00:00.000
5	EM	0	Ms.	Gail	A	Erickson	NULL	0	NULL	<IndividualSurvey xmlns="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/IndividualSurvey"><TotalPurchaseYTD>0</TotalPurchaseYTD></IndividualSurvey>	F3A3F6B4-AE3B-430C-A754-9F2231BA6FEF	1998-01-30 00:00:00.000

I’ve only shown the first five rows of data that were returned from the database but there are actually 19972 rows that are returned if you run the query as it is written.  While the query if fast to write, it isn’t always the best choice since it causes a lot of data to have to be processed and unless you actually need every column you should choose to select only the required columns for your application.  For example, suppose you only wanted the first and last name of the people in your table.  Here is the SELECT query:

SELECT FirstName, LastName FROM AdventureWorks2008.Person.Person

Results

FirstName	LastName
Syed	Abbas
Catherine	Abel
Kim	Abercrombie
Kim	Abercrombie
Kim	Abercrombie
Hazem	Abolrous
Sam	Abolrous
Humberto	Acevedo
Gustavo	Achong
Pilar	Ackerman
Pilar	Ackerman
Aaron	Adams
Adam	Adams
Alex	Adams
Alexandra	Adams

I’ve only shown the first 15 names but this query returns the same number of rows as the previous query 19972.  All we’ve done is reduce the columns to the necessary ones.  What if we only wanted the first 100 rows?  Simple:

SELECT TOP 100 FirstName, LastName FROM AdventureWorks2008.Person.Person

Notice the TOP 100 right after the SELECT command.  That tells SQL Server to only pull the first 100 records.  What if we wanted to sort by FirstName?  This requires some new keywords ORDER BY.

SELECT TOP 15 FirstName, LastName FROM AdventureWorks2008.Person.Person ORDER BY FirstName;

I’m selecting the first 15 rows.  The default sort order is ascending.  Here are the results:

FirstName	LastName
A.	Leonetti
A.	Wright
A. Scott	Wright
Aaron	Adams
Aaron	Alexander
Aaron	Allen
Aaron	Baker
Aaron	Bryant
Aaron	Butler
Aaron	Campbell
Aaron	Carter
Aaron	Chen
Aaron	Coleman
Aaron	Collins
Aaron	Con

What if you want to sort descending?  Use the keyword DESC (which stands for descending).  There is a keyword for ascending as well…ASC.

SELECT TOP 15 FirstName, LastName FROM AdventureWorks2008.Person.Person ORDER BY FirstName DESC;

Ok folks, those are the essentials of the SQL Server SELECT command.  I’ve really only touched the surface of the capabilities of the SELECT command but the goal of this post was to expose you to the basics.  I’ll be writing more on the deeper details later.

Valid for SQL Server 2005, 2008, R2, 2012, 2014.

How to use Transact-SQL DEALLOCATE with Examples – 2005, 2008, R2, 2012, 2014

Topic: Transact-SQL DEALLOCATE

The purpose of the DEALLOCATE keyword in sql server is to remove a cursor reference.  SQL Server has data structures behind the scenes that are released once DEALLOCATE is executed.

Syntax

DEALLOCATE { { [ GLOBAL ] cursor_name } | @cursor_variable_name }


Example

-- SAFEGUARD
-- not familiar with the .. syntax below?  check out this blog <a title="dbo .. syntax and the default database" href="http://examplesql.com/sqlserver-tsql/dbo-dotdot-syntax/" data-mce-href="http://examplesql.com/sqlserver-tsql/dbo-dotdot-syntax/">post</a> 
IF OBJECT_ID('tempdb..#Hobbies') IS NOT NULL
BEGIN
    DROP TABLE #Hobbies
END

-- create the temp table
CREATE TABLE #Hobbies (
	id INT IDENTITY(1,1) NOT NULL,
	article_name NVARCHAR(100)
)

-- fill the temp table with sample data
INSERT INTO #Hobbies (article_name)
VALUES 
('cooking'),('crafts'),('flying'),
('T-SQL'), ('wood carving'),('gardening'),
('reading'),('beer brewing'),('gaming');

SELECT article_name FROM #Hobbies;

-- create the variable we'll use to store data from the FETCH
DECLARE @articleName NVARCHAR(100);

------------------ CURSOR SPECIFIC CODE BEGIN --------------------
-- declare the fast_forward cursor.  notice we are essentially
-- using a SELECT query to build a list to iterate through
DECLARE hobbiesCursor SCROLL CURSOR FOR
SELECT article_name FROM #Hobbies ;

-- now we have to open the cursor and tell it to go
-- acquire (i.e. FETCH) items from the temp table
OPEN hobbiesCursor
FETCH FIRST FROM hobbiesCursor INTO @articleName;
SELECT ('First Hobby Name: ' + @articleName );	
FETCH NEXT FROM hobbiesCursor INTO @articleName;
SELECT ('Second Hobby Name: ' + @articleName );	
FETCH LAST FROM hobbiesCursor INTO @articleName;
SELECT ('Last Hobby Name: ' + @articleName );
FETCH PRIOR FROM hobbiesCursor INTO @articleName;
SELECT ('Second to Last Hobby Name: ' + @articleName ) ;	

CLOSE hobbiesCursor ;
DEALLOCATE hobbiesCursor;

Results

(9 row(s) affected)
article_name
----------------------------------------------------------------------------------------------------
cooking
crafts
flying
T-SQL
wood carving
gardening
reading
beer brewing
gaming

(9 row(s) affected)

----------------------------------------------------------------------------------------------------------------------
First Hobby Name: cooking

(1 row(s) affected)

-----------------------------------------------------------------------------------------------------------------------
Second Hobby Name: crafts

(1 row(s) affected)

---------------------------------------------------------------------------------------------------------------------
Last Hobby Name: gaming

(1 row(s) affected)

-------------------------------------------------------------------------------------------------------------------------------
Second to Last Hobby Name: beer brewing

(1 row(s) affected)

Notice DEALLOCATE is at the very bottom of the code listing.  It’s role is simply to perform memory ‘clean up’.  A LOCAL cursor variable does not have to be deallocated since it freed when the variable goes out of scope (end of the batch, stored procedure, or trigger), however GLOBAL cursors should be freed unless you intentionally mean to reuse the cursor during the course of the entire database connection.  Additionally, If you are planning to reuse a cursor variable multiple times in your scope then you should deallocate the cursor variable as required.

Example SQL

USE AdventureWorks2008;
GO

DECLARE @PersonCursor CURSOR
SET @PersonCursor = CURSOR LOCAL SCROLL FOR
SELECT * FROM Person.Address;

DEALLOCATE @PersonCursor;

SET @PersonCursor = CURSOR LOCAL SCROLL FOR
SELECT * FROM Person.EmailAddress;
GO

/* CURSOR IS AUTOMATICALLY DEALLOCATED 
WHEN IT GOES OUT OF SCOPE */

For some of the deeper details of DEALLOCATE you can check out the documentation here.

Valid for SQL Server 2005, 2008, R2, 2012, 2014.

TSQL DEALLOCATE T-SQL DEALLOCATE SQL SERVER DEALLOCATE

TSQL DEALLOCATE T-SQL DEALLOCATE SQL SERVER DEALLOCATE EXAMPLE CODE

How to Declare and Use the MySQL DECIMAL Data Type

What is a MySQL DECIMAL?  Simply put, it is just a number that can have a decimal in it (2012.56 and -2013.0034 are examples).  Let’s take a look at how to declare a MySQL DECIMAL.

DECIMAL(M, D)

M is the maximum number of digits (IE precision) and has a range from 1 to 65 (Take note that versions of MySQL prior to 5.0.3 allowed the range from 1 to 254).  This is the total number of digits INCLUDING decimal digits.

D is the number of digits to the right of the decimal point (IE scale) and has a range from 0 to 30 AND cannot be larger than M.

Why use a MySQL DECIMAL?

You would generally use a decimal type when you need to store exact fractional values like money.  It doesn’t suffer from the rounding errors of other number types in MySQL.

How do you use MySQL DECIMAL?

Here is some example mysql code…

CREATE DATABASE IF NOT EXISTS Testing;
USE Testing;
CREATE TABLE WeightCalculation (WeightCalculationID INT NOT NULL, Weight DECIMAL(10,5) NOT NULL);
INSERT INTO WeightCalculation (WeightCalculationID, Weight) VALUES (1,54.3445);
INSERT INTO WeightCalculation (WeightCalculationID, Weight) VALUES (2,928.23017);
SET @a = (SELECT SUM(WEIGHT) FROM WeightCalculation);
INSERT INTO WeightCalculation (WeightCalculationID, Weight) VALUES (3,@a);
SELECT * FROM WeightCalculation;
DROP DATABASE Testing;

Results

WeightCalculationID|Weight
1	54.34450
2	928.23017
3	982.57467

So let walk through this code and see what is going on.  To start, I create our Testing database if it doesn’t exist.  Then I create a table called ‘WeightCalculation’ and give it two columns ‘WeightCalculationID’ and ‘Weight’ in order to store some simple data.  Notice that column ‘Weight’ has been declare a DECIMAL of total length 10 digits and up to 5 decimal places.  Next, I insert two rows of data into the table.  Just for fun I calculate the sum of all the Weight column values and store them in a user-defined variable named @a then insert the sum into another row of the table.  Lastly, I perform a SELECT operation on the table to get it’s contents.  To clean up I drop the Testing database.

For further information check here.  Check here for more examples of precision math.

How to declare and use MySQL DECIMAL

How to declare and use MySQL DECIMAL