Skip to main content

SQL SERVER : Selecting data from temporary tables & table variables using FOR XML

We can
convert the relational data stored in the table into XML by using the FOR XML
syntax, I am not going to the explain all the features of FOR XML.



Physical table


SELECT * FROM ASPNET_Roles FOR XML AUTO,ROOT ('A'),ELEMENTS

this select statement will give the following output

<A><URR_ASPNET_Roles>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>89C306A6-2D21-42AB-A42F-5029091CB4E8</RoleId>
<RoleName>SBU
User</RoleName>
<LoweredRoleName>sbu
user</LoweredRoleName>
<USER_TYPE>2</USER_TYPE>
</URR_ASPNET_Roles>
<URR_ASPNET_Roles>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>180BA05D-D2A5-49CA-BED3-3C6F080F6543</RoleId>
<RoleName>Super
User</RoleName>
<LoweredRoleName>super
user</LoweredRoleName>
<USER_TYPE>1</USER_TYPE>
</URR_ASPNET_Roles>
</A>


its is a perfect xml with all the nodes and 'A' as the root element

now consider selecting the data from temporary table & table variable


SELECT *
INTO #TBL_TMP FROM
ASPNET_Roles

the values of the table URR_ASPNET_Roles is inserted into temporary table #TBL_TMP

SELECT *
FROM #TBL_TMP FOR
XML AUTO,ROOT('A'),ELEMENTS

the above select statement will produce the following output

<A>
<_x0023_TBL_TMP>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>89C306A6-2D21-42AB-A42F-5029091CB4E8</RoleId>
<RoleName>SBU
User</RoleName>
<LoweredRoleName>sbu
user</LoweredRoleName>
<USER_TYPE>2</USER_TYPE>
</_x0023_TBL_TMP>
<_x0023_TBL_TMP>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>180BA05D-D2A5-49CA-BED3-3C6F080F6543</RoleId>
<RoleName>Super
User</RoleName>
<LoweredRoleName>super
user</LoweredRoleName>
<USER_TYPE>1</USER_TYPE>
</_x0023_TBL_TMP>
</A>


but what is _x0023_
doing in output, from where did it originate ? how can we remove this
addition in the xml tag

consider the following statement

SELECT *
FROM #TBL_TMP TBL_TMP
FOR
XML AUTO,ROOT('A'),ELEMENTS

this will produce the following output

<A>
<TBL_TMP>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>89C306A6-2D21-42AB-A42F-5029091CB4E8</RoleId>
<RoleName>SBU
User</RoleName>
<LoweredRoleName>sbu
user</LoweredRoleName>
<USER_TYPE>2</USER_TYPE>
</TBL_TMP>
<TBL_TMP>
<ApplicationId>AFFE3DDD-ABAD-49DF-A144-DA87BE69B90E</ApplicationId>
<RoleId>180BA05D-D2A5-49CA-BED3-3C6F080F6543</RoleId>
<RoleName>Super
User</RoleName>
<LoweredRoleName>super
user</LoweredRoleName>
<USER_TYPE>1</USER_TYPE>
</TBL_TMP>
</A>

the output is clean with no extra additions !!!

How ? in the second statement we have provided an alias for the table which is
displayed in the output

same is the case with table variable's

DECLARE @tblVar TABLE
(ID INT,DATA
VARCHAR(10))

INSERT INTO @tblVar
VALUES (1,'DATA1')

SELECT *
FROM @tblVar FOR
XML AUTO,ROOT('A'),ELEMENTS

<A>
<
_x0040_tblVar>
<ID>1</ID>
<DATA>DATA1</DATA>
</
_x0040_tblVar>
</A>

SELECT *
FROM @tblVar TBLVAR FOR
XML AUTO,ROOT('A'),ELEMENTS

<A>
<TBLVAR>
<ID>1</ID>
<DATA>DATA1</DATA>
</TBLVAR>
</A>


why are such additional unwanted strings displayed in temporary tables and table
variables and not in the case of physical tables

temporary tables and table variables have # & @ attached to their names
respectively, so these special characters are parsed by SQL server and converted
into xml, in both cases we can remove these unwanted additions by using aliases.


Happy programming

Comments

Popular posts from this blog

Product Backlog: Should you write everything in user story format?

I like user stories a lot. They help everyone talk the same language and results in a better product. User story alone does not constitute product requirement. User story is supposed to be a place holder for discussion which should happen between the team, Product Owner and the customer. This discussion result in a common understanding which along with the user story content is the product requirement. This format captures the essence of requirement without confusing the readers User Story is only one of the many different ways in which requirements can be represented. This is not mandatory in any Agile “process”. But many have made this mandatory. I have seen many spending countless hours trying to write the requirements in user story format when they could have easily written that in simple one-line sentence in few minutes.   I have seen team members refusing to even discuss the requirement until product owner rewrote the requirement in user story format. ...

PDCA & SCRUM (or Agile); Why is it important?

The PDCA (Plan DO Check Act) cycle was made popular by Dr. W. Edwards Deming. This is a scientific cyclic process which can be used to improve the process (or product). This is cyclic in nature and usually time boxed. Plan  This is the first stage of the process. During this step the team discusses the objectives, the process and the clear conditions of exit (conditions of acceptance). This stage sets the measurable and achievable goals for the team. DO Team works together to achieve the objective set in the planning phase. Team works with the set of agreed process. Check Once the implantation is done team regroups and verifies the output and compares it to the agreed conditions of acceptance decided during the planning phase. The deviation, if any, is noted down. ACT If any deviation in planned tasks is observed during the Check stage, a root cause analysis is conducted. Team brainstorms and identifies the changes required to prevent such deviatio...

SQL Server: GETDATE() & GETUTCDATE() & different time zones

Most of us will use GetDate() function for providing default value in SQL server columns. This function Returns the current database system timestamp as a   datetime   value without the database time zone offset. This value is derived from the operating system of the computer on which the instance of SQL Server is running. This works perfectly if you don’t have to show reports and such stuffs for users from different time zones. In case you want to store time independent of time zones in some universal format; what will do? Well there is GetUtcDate() function for you. This function will return then UTC date based on the setting of the server on which SQL server is installed. I executed the following function & I got the two different date output values. SELECT  GETDATE() AS Expr1, GETUTCDATE () AS Expr2 2/28/2010 1:27:17 PM ,  2/28/2010 7:57:17 AM SQL Server 2008 SQL Server 2008 has two new DataTypes: date & time You can use them to ret...