Compound Operators in SQL Server

July 5, 2011 1 comment

There was a time when we all wished SQL Server supports compound operators just like any other programming languages. Wouldn’t it be nice to have a shorter syntax for assigning the result of an arithmetic operator?  Well, SQL server 2008 introduced Compound operators that allow you to perform several arithmetic operations using an operand along with equal to (=) operand.

 For example:

Declare @var1  int

Set @var1 = 150

Set @var1 += 100

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Understanding MERGE Transact SQL Statement

July 5, 2011 1 comment

By using “Merge”, you can perform insert, delete and update on a table in a single SQL statement. This helps in synchronizing the tables as well.

However while using merge there are several points that you need to keep in mind. Few

  • In a “Merge” statement, a “When Matched” clause with a search condition cannot appear after a ‘When Matched’ clause with no search condition.
  • A “Merge” statement must be terminated by a semi-colon (;).
  • An action of type ‘DELETE’ is not allowed in the ‘WHEN NOT MATCHED’ clause of a MERGE statement.
  • At least one of the three MATCHED clauses must be specified, but they can be specified in any order. A variable cannot be updated more than once in the same MATCHED clause.
  • Any insert, update, or delete actions specified on the target table by the MERGE statement are limited by any constraints defined on it, including any cascading referential integrity constraints.

Few examples of merge are as given below.

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SSIS : Sequence Container

July 5, 2011 Leave a comment

Sequence containers is used to group the package into multiple separate control flows, each containing one or more tasks and containers that run within the overall package control flow. There are several advantages in using sequence container

  1. Provides facility to set property of multiple tasks by setting the property of sequence container.
  2. Provides the facility of disabling groups of tasks to focus debugging on one subset of the package control flow.
  1. Scope for variables that a group of related tasks and containers use can be controlled easily.
  2. Managing and visualization of group of tasks becomes easier using sequence container.
  3. We can also expand and collapse the container, hence making the package look neat.

Using Sequence Container

Create a new SSIS package ( refer video to create new SSIS package). Drag the sequence container from the toolbox on the left hand side into the package.

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Creating Excel Files (.xls) dynamically from SSIS

April 25, 2011 1 comment

In this blog, I will walk you through the creation of excel files ( xls / Excel 2003)  dynamically through SSIS.

Scenario: every day one of my process runs to pull data from SQL server table to excel file. I need to use unique file everyday with name as “taxonomy_<date>.xls” , for example on 14th of January 2011 the file name should be “Taxonomy_01142011.xls” with the excel sheet name “TaxonomyValues”.

It is pretty simple to create this file dynamically. At first we need to set up an excel connection manager pointing to the file. The connection manager needs to be dynamically configured to point to the correct file everyday, in our case “Taxonomy_01142011.xls” on 14th Jan. To do this,

  1. go to properties window of the excel connection manager
  2. click on expression and the browse ( … symbol) and choose “excel File Path” property. ( please refer the pictures below)
  3. Copy and paste the expression given below or develop similar expression. Click on evaluate expression and it will display the file path as evaluated value.

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The string function SOUNDEX() and its purpose in SQL.

April 25, 2011 Leave a comment

The Soundex code was developed to help negate the effects of all the spelling variations that can occur for similar sounding names ( Smith, Smithe, Smythe, etc.).  This way, users can index records based on a Soundex code based on the sound  and “not” by how it is spelled.

The Soundex system is not infallible – the surnames Gough and Goff sound the same (Goff), but a different code is formed for these two names.  Soundex can however be used to a great extent to get a desired result ( atleast closer to a desired result) This is a commonly used algorithm by many researchers.

In SQL a string function is available for this and is usually comes handy.  The function is

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Executing the script in batch file using “sqlcmd” command

April 25, 2011 1 comment

 often create batch files to execute sql scripts ( specially SPs) and then schedule it using SQL agent job/Task Scheduler. In this post , I will show you how to create a batch file with sql commands.

First of all, The command that is used to execute SQL queries from commnd prompt is “SQLCMD“. The general syntax of this command is available in the link. I will go with a simple one as below

sqlcmd –E –S Servername –Q Query -o “Output Path”

here
-E = Trusted connection (windows authentication)
-S = Server Name
-Q = CommandLineQuery
-o = Output file path
a simple command on the commnad prompt can be written as
 
 
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Changing SQL database to single user mode and back to Multi User mode

October 26, 2010 1 comment

It is often necessary to change the database to single user mode, especially if you are a DBA. A simple example would be to change the collation settings or any DB settings. The single user will allow only one  user ( usually DBA) to access the database. Hence it will be easy to make changes without the worry of deadlocks or any other type of contention for DB and also without affecting the users.

It is very easy to change the database to Single user mode; in fact, it is just an execution of the script away. Use the script below to change the mode.

ALTER  DATABASE <<Database Name>>  SET SINGLE_USER  WITH NO_WAIT

The NO_WAIT clause will set it to single user mode as soon as you execute the query.  An alternate to this is by using the system stored procedure sp_dboption

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