Welcome to SQLServer MVP Blog

Venkatesan Prabu MCITP,MCAD,MCTS,CCNA. Worked as a ProjectLead(Senior .Net developer,SQL DBA). Now, Managing Director of KAASHIV INFO TECH, Chennai This Blog aims in serving the community in a better way. This blog is read by developers in 159 countries with average of 400 hits per day. Please post your valuable suggestions and hold my hand to serve the community. Lets make a new world with good thoughts and good minds....... This blog serves the SQL server community all over the world.

22.10.08

Len Vs Datalength in sql server

I have seen a very common question like, Whats the difference between len and datalength function in SQL Server? (Important Interview question too... )

I have created a table name 'VENKATTABLE'

CREATE TABLE VENKATTABLE(NAME VARCHAR(100))
INSERT INTO VENKATTABLE VALUES('VENKAT ')
SELECT * FROM VENKATTABLE

Now, I've tried to use these statements,

SELECT LEN(NAME) FROM VENKATTABLE -- OUTPUT =>6
SELECT DATALENGTH(NAME) FROM VENKATTABLE -- OUTPUT =>9

The difference is length will trim the data and it wont consider the spaces available. Whereas, Datalength will fetch the exact data available and it will consider the spaces too.

In this case, I've tried with Ltrim and Rtrim to achieve the same functionality of len function.

SELECT DATALENGTH(LTRIM(RTRIM(NAME))) FROM VENKATTABLE -- OUTPUT =>6

Happy Learning!!!
Regards,
Venkatesan Prabu .J

Tamil Joke - If we got chance to speak truth in interview

வேலைக்கான நேர்காணலில் ... உண்மையைச் சொல்ல முடிந்தால் ....

நீங்கள் ஏன் எங்கள் நிறுவனத்தில் பணிபுரிய விரும்புகிறீர்கள் ..?

எந்தப் புண்ணாக்குக் கம்பெனியிலாவது வேலை செஞ்சாதான் பொழப்ப ஓட்ட முடியும்.. எந்த நாய் வேலை குடுக்குதோ அங்க வேலை செய்ய வேண்டியதுதான் .. அதைத் தவிர உன் கம்பேனி மேல பெருசா ஒண்ணும் மதிப்பு மரியாதையெல்லாம் இல்லே ..!

உங்களுக்கு ஏன் இந்த வேலையைத் தரவேண்டும் ..?
உன் கம்பெனி வேலையை யாராவது ஒருத்தன் செஞ்சுதானே ஆகணும்... என்கிட்டதான் கொடுத்துப் பாரேன்.

உங்களுடைய தனித்திறமை என்ன ..?

வேலைக்கு சேர்ந்ததும் , கடலை போட வழியிருக்கான்னு பார்ப்பேன்.. இங்கேருந்து என்னென்ன சுடலாம்ன்னு நோட்டம் உடுவேன் .. உன் கம்பெனியில் வேலைக்கு சேர்ந்ததைச் சொல்லி ஊர் பூரா கடன் வாங்குவேன்.. அப்புறம் வேற கம்பெனிக்கு தாவ முயற்சி பண்ணுவேன் .. இதைத் தவிர உன் கம்பெனிக்கு சேவை செஞ்சு முன்னுக்குக் கொண்டு வரணும்ங்கிற மூட நம்பிக்கையெல்லாம் கிடையாது .

உங்கள் மிகப்பெரிய பலம்..?
இதைவிட பெரிய சம்பளத்தில் வேலை கிடைச்சா அப்படியே உட்டுட்டு அங்கே ஓடிருவேன் .. மனசாட்சி, நன்றியுணர்வு இதுக்கெல்லாம் முட்டாள்தனமா ,, இடமே கொடுக்காம கடுமையா நடந்துக்குவேன் ..

பலவீனம்..?

ஹி.. ஹி... பெண்கள்..!

இதற்கு முன் வேலை பார்த்த நிறுவனத்தில் உங்கள் சாதனைகள் என்ன..?அப்படி ஏதும் இருந்தா நான் ஏன் வேலை தேடி இங்கே வருகிறேன் .. அந்த சாதனைகளை பெருசா பில்டப் பண்ணி அங்கேயே வேணும்ங்கிற அளவுக்கு சம்பளத்தைக் கறந்துருக்க மாட்டேனா ..?

நீங்கள் சந்தித்த மிகப்பெரும் சவால் என்ன ..?

அதை எப்படி வெற்றி கொண்டீர்கள் ..?ஆண்டவன் அருள்தான் காரணம்.. இதுவரைக்கும் எந்த நிர்வாகியும் மூணாவது மாசச் சம்பளத்தைக் கொடுக்கறதுக்கு முன்னே நான் ஒரு வெத்துவேட்டுன்னு கண்டுபிடிச்சதே இல்லே .

ஏன் இதற்கு முன் பார்த்த வேலையை விட்டு விட்டீர்கள் ..?
நீங்கள் ஏன் இந்த வேலைக்கு நேர்காணல் நடத்த வேண்டிய அவசியம் வந்ததோ.. அதே காரணத்துக்காகத்தான்..!

இந்த பதவியில் நீங்கள் எதிர்பார்க்கும் அம்சங்கள் என்ன..?

நல்ல சம்பளம் , 0 % வேலை, பக்கத்து சீட்டுல கண்ணுக்கு குளிர்ச்சியா ஒரு பெண் , நாட்டாமை பண்ண எனக்குக் கீழே ஒரு கூட்டம். அது போதும் .
Endrum
Venkat,

17.10.08

Social article - Software Companies firing employees

Often, we are hearing a frequent new about software down due to financial break down in US.
I got some information on recent happenings in software field.

HP Layoffs

HP 24000 Lay-offs - After acquiring EDS, HP is planning to reduce their work force and they planned to take out 24000+ employees from their company. It includes both higher level and lower level people.

Satyam 4500 Job cuts :
Due to lehman brothers closure, Satyam computers has just started giving pink slips to its employees, could potentially downsize its workforce by a whopping 4,500 employees. Recently, satyam head have informed their employees not to be panic and advising his people to work hard.

Wipro technologies started giving pink slips:
Wipro technologies has put about 4-5% of its workforce, about 2,400-3,000 employees, under the scanner for non-performance.
This is the cycle and everyone has to sustain this problem. If you see the past 10 years record of IT industry it got changed in 2-3 times majorly in 2003. Satyam and Wipro are service based companies if their client is going to the depth of loss then why they bare the loss it is obvious that they will fired the employees.
The recent IT Lay offs is mainly due US Market slowdowns. And as everyone of us knows that the market is never stable. Who knows that though it is down now, it may grow at a remarkable height.
This is once again the firing season for IT. Satyam Computers has just started giving pink slips to its employees and around 4,500 of its employees are scheduled to get the boot.

wipro firing
Wipro Technologies has put about 4-5% of its workforce or about 2,400-3,000 employees, under the scanner for non-performance.
tcs firing
In February, TCS had given pink slips to 500 non-performers.

IBM firing
IBM India also asked about 700 employees to leave, citing non-performance.

patani firing
In July, Patni computer systems fired 400 employees.
If the going is tough for these bigwigs, what about those in the lower rung? Mid tier companies are also doling out pink slips in all generosity! Hexaware has reportedly booted out 500 people and this does not include the 130 employees to be laid off due to the shut down of its office in Gurgaon. Ramco Systems laid off 142 employees.
Not true news on infy firing.

Reference:

http://www.alleyinsider.com/2008/9/hp-firing-24-600-employees-after-buying-eds-hpq-

http://hubpages.com/hub/Indian-IT-Companies-Infy-Wipro-Satyam-Cognizant-Accenture-IBM-Firing-News

http://topinews.com/story/title/wipro-firing-infyosys-firing-cts-firing--hp-firing--news

http://www.indyapulse.com/Blogs/View.asp?ArticleId=688&CatId=111

Kindly share your comments regarding this post.
Regards,
Venkatesan Prabu .J

11.10.08

Social article - Increase in price - In india

Increase in rates:

Everywhere rates were increasing due to some of our people. They are ready to pay huge money for lemon juice too. I have seen some hotels were selling lemon juice at Rs. 20. Are we think about the money which we are spending is worth. (50 paise to 1 Rs Lemon + 1 Rs sugar +1 Rs water +1 Rs Electricity). Why dont we prepare a lemon juice in our home. Are we become too lethargic.
Giving huge tips to servers in the hotel. They are expecting the same from the normal people and they are not ready to serve the normal people. Dont you think, we are taking our society to the wrong side. We will raise flags against bribes. But, every one of us were doing the same indirectly.
For comfortness, we used to book and travel in A/C buses. Monday morning, I have to go to job and I should not feel tired. Sunday nights, all ticket rates got increased and normal people cant travel in ordinary deluxe bus too. We are ready to buy tickets in black and indirectly, most of us spoiled our society. You can ask me, Why venkat is pointing only software engineers. Its because, we are now becoming educated fools... for getting comfortness. Nowadays, Black tickets for movies were increasing. Even theatre people stopped to give tickets in counter. Inturn, they are arranging poeple and selling their tickets for good rates.
Our people wish to see films only in Mayajaal, INOX and other big theatres. Atleast, we should think about wasting our percious money. Some of us will go rarely to watch good films. Some of our people will prefer only those hi-fi theatres. Because they need comfortness to sit for 3 hours. Please please think whether we are spending our money for worthful things.

Planning to buy a house in India :-( Check this URL,

http://venkattechnicalblog.blogspot.com/2008/10/social-article-buy-property-in-india.html

How we are going to stop this? Provide me more inputs on this topics?

Venkatesan Prabu .J

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SQL Server Interview questions - Part 1

What is the significance of NULL value and why should we avoid permitting null values?
Null means no entry has been made. It implies that the value is either unknown or undefined.We should avoid permitting null values because Column with NULL values can't have PRIMARY KEY constraints. Certain calculations can be inaccurate if NULL columns are involved.

What is SQL whats its uses and its component ?
The Structured Query Language (SQL) is foundation for all relational database systems. Most of the large-scale databases use the SQL to define all user and administrator interactions. It enable us to retrieve the data from based on our exact requirement. We will be given a flexibility to store the data in our own format.

The DML component of SQL comprises four basic statements:
* SELECT to get rows from tables
* UPDATE to update the rows of tables
* DELETE to remove rows from tables
* INSERT to add new rows to tables

What is DTS in SQL Server ?
Data Transformation Services is used to transfer the data from one source to our required destination. Considering am having some data in sql server and I need to transfer the data to Excel destination. Its highly possible with dialogue based tool called Data Transformation services. More customization can be achieved using SSIS. A specialized tool used to do such migration works.

What is the difference between SQL and Pl/Sql ?

Straight forward. SQL is a single statement to finish up our work.Considering, I need some data from a particular table. “Select * from table” will fetch the necessary information. Where as I need to do some row by row processing. In that case, we need to go for Procedural Logic / SQL.

What is the significance of NULL value and why should we avoid permitting null values?
Null means no entry has been made. It implies that the value is either unknown or undefined.We should avoid permitting null values because Column with NULL values can't have PRIMARY KEY constraints. Certain calculations can be inaccurate if NULL columns are involved.

Difference between primary key and Unique key?
Both constraints will share a common property called uniqueness. The data in the column should be unique. The basic difference is,
· Primary key won’t allow null value. Whereas, unique key will accept null value but only one null value.
· On creating primary key, it will automatically format the data inturn creates clustered index on the table. Whereas, this characteristics is not associated with unique key.
· Only one primary key can be created for the table. Any number of Unique key can be created for the table.

SQL Server Interview Question - Part 2

What is normalization?

Normalization is the basic concept used in designing a database. Its nothing but, an advise given to the database to have minimal repetition of data, highly structured, highly secured, easy to retrieve. In high level definition, the Process of organizing data into tables is referred to as normalization.

What is a stored procedure:
Stored procedures are precompiled T-SQL statements combined to perform a single task of several tasks. Its basically like a Macro so when you invoke the Stored procedure, you actually run a set of statements. As, its precompiled statement, execution of Stored procedure is compatatively high when compared to an ordinary T-SQL statement.

What is the difference between UNION ALL Statement and UNION ?
The main difference between UNION ALL statement and UNION is UNION All statement is much faster than UNION,the reason behind this is that because UNION ALL statement does not look for duplicate rows, but on the other hand UNION statement does look for duplicate rows, whether or not they exist.

Example for Stored Procedure?
They are three kinds of stored procedures,1.System stored procedure – Start with sp_2. User defined stored procedure – SP created by the user.3. Extended stored procedure – SP used to invoke a process in the external systems.Example for system stored proceduresp_helpdb - Database and its propertiessp_who2 – Gives details about the current user connected to your system. sp_renamedb – Enable you to rename your database

What is a trigger?

Triggers are precompiled statements similar to Stored Procedure. It will automatically invoke for a particular operation. Triggers are basically used to implement business rules.

What is a view?
If we have several tables in a db and we want to view only specific columns from specific tables we can go for views. It would also suffice the needs of security some times allowing specfic users to see only specific columns based on the permission that we can configure on the view. Views also reduce the effort that is required for writing queries to access specific columns every time.

What is an Index?
When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index.

What are the types of indexes available with SQL Server?

There are basically two types of indexes that we use with the SQL ServerClustered -

1. It will format the entire table, inturn physically sort the table.

2. Only one clustered index can be created for a table.

3. Data will be located in the leaf level.

4. By default, primary key will create clustered index on the table.

Non-Clustered Index

1. It wont touch the structure of the table.

2. It forms an index table as reference to the exact data.

3. A reference to the data will be located in the leaf level.

4. For a table, we can create 249 non clustered index.

Happy Learning!!!
Regards,
Venkatesan Prabu .J

SQL Interview question

Extent Vs Page?

Pages are low level unit to store the exact data in sql server. Basically, the data will be stored in the mdf, ldf, ndf files. Inturn, pages are logical units available in sql server.The size of the page is 8KB.

Eight consecutive pages will form an extent 8 * 8KB = 64KB.

Thus I/O level operation will be happening at pages level.The pages will hold a template information at the start of each page (header of the page).

They are,

1. page number,

2. page type,

3. the amount of free space on the page,

4. the allocation unit ID of the object that owns the page.

Extents will be classifed into two types,

1. Uniform extents

2. Mixed extents

Uniform Extents:It occupied or used by a single object. Inturn, a single object will hold the entire 8 pages.Mixed

Extents:Mulitple objects will use the same extent. SQL Server will allow a max of eight objects to use a shared extent.

Property of SQL Server :Initally if an object is created, sql server will allocate the object to the mixed extent and once if the size reaches 8 pages and more... immediately, a new uniform extent will be provided for that particular object.

Herecomes, our fragmentation and reindexing concepts.