Here are the list of options that can help you in deciding and managing high availabilty options in SQL Server 2008

Increased Availability

• Database Mirroring
• Log Shipping
• Failover Clustering
• Geographically Dispersed Failover Clustering
• Peer-to-Peer Replication

Decreased Downtime

• Fast Database Recovery
• Backup and Restore
• Checksum on Data Pages
• Online Index Operations
• Online, Piecemeal, and Page-Level Restore
• Partial Database Availability
• Snapshot Isolation

Dynamic Configuration

• Enhanced Manageability
• Database Snapshots
• Table and Index Partitioning
• Backup and Restore
• Dedicated Administrator Connection
• Resource Governor

for More info please check the white paper of Microsoft SQL Server 2008 High Availabilty – Always on Technologies
http://www.microsoft.com/sqlserver/2008/en/us/wp-sql-2008-high-availability.aspx

SQL Server Code Name

Yesterday, I came across a very interesting question on one of the SQL Servers Online Forums.

Question – What is the code name of SQL Server 2005?

Well I knew that the Microsoft gives code names to it products when they are in developmental stages. But I never came across the code name for SQL Serves!

So I did some research on Net to find code name of all the SQL Server Release till date. They are listed below.

Good Luck!

In SQL Server, whenever we create any key, a Primary Key automatically creates clustered index on the same. I like this feature and I use this feature every now and then.

The question is does the change of any column as Primary Key should also create a Clustered Index? Moreover, is there any case, where one would not do the same?

One of the recent conversations I had with one SQL Expert is with regard to the SSN number. The discussion was that SSN numbers are always unique and never repeated and hence are the best candidates for primary key. Additionally SSN numbers contains dashes (-), which make the datatype of the SSN numbers as String (VARCHAR or NVARCHAR). A clustered index on an integer usually performs better over a clustered index on an integer and makes the DBA to choose Primary Key of datatype Integer. At one point in our conversation, we discussed that if SSN number should be a Unique Constraint and if there should be another Identity Column as the Primary Key.

Some of the questions from our interesting discussion are as follows:

Would you have the datatype of your Primary Key as string?
Would you treat SSN as string datatype or remove the dashes and change it into an integer?
Do you have a real life example, where your primary key is not a clustered index?
What are the best practices for SSN number to store in database and obtain optimal performance?

I will post an interesting answer discussing this subject in a separate post with due credit.

Reference: Pinal Dave (http://blog.sqlauthority.com)

I quite often get request to summarized my ideas about Removing bookmark lookup on this blog post. Bookmark lookup or key lookup are bad for any query as they force query engine to lookpup corresponding row in the table or index as it does not find required data from just reading the data.

Here are list of my four post written on the same subject.

SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup

SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 2

SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 3

SQL SERVER – Removing Key Lookup – Seek Predicate – Predicate – An Interesting Observation Related to Datatypes

Let me know your opinion about the same and I am interested to here what you have to add to this subject.

Reference: Pinal Dave (http://blog.sqlauthority.com)

Expert SQL Server 2008 Encryption (Paperback)
Michael Coles (Author), Rodney Landrum (Author)

Link to Amazon

“What is your opinion on encryption? What I mean is: In a world filled with data, how do you see encryption?” This is the precise question Michael Coles posed to me on March 3^rd of this year, while we were heading to Starbucks in Seattle. We were both attending the Microsoft MVP Summit there.

In the information era, security has become one of the most vital aspects of life. Although the topic may seem a little mundane, its importance cannot be overemphasized. It is the pillar of the information age and I shudder to think where we would be without it. We don’t leave our houses unlocked and risk thieves or opportunists taking off with our valuables. We also often take precautions, not only to preserve the precious, but also to avoid the sheer hassle of replacement and misuse. So too it should be with our information.

Encryption’s roots are extremely old and it has resolved numerous security problems over the years. In days gone by, couriers were entrusted with letters sealed with a royal wax stamp. If on delivery, the seal was broken, it was obvious that there had been a security breach. This very concept evolved as CRC checksum and developed into a complex algorithm.  While CRC checksum alerted the end user to the fact that content had been modified, its limitation was that it allowed manipulation of the content to occur in the first place. With encryption, only the authenticated owner can access and modify content.

In response to Michael’s question, I began to tell him what I knew about public and private keys. He looked at me doubtfully and asked me directly if I had ever used encryption in my career. My reluctant answer to this was “No”. He strongly suggested that I not underestimate its capabilities and explore its possibilities. I took his advice and have since implemented encryption for many of my clients, who are now far safer from unauthorized access to data.

To be very honest, in my experience, not many people know much about the subject beyond a little about public and private keys.  You do not often find experts discussing symmetric and asymmetric keys, which are just the tip of the iceberg. SQL Server has come a long way with regard to security. Encryption has taken on a whole new meaning in SQL Server 2008. There are many new features such as Extensible Key Management, Transparent Data Encryption, not to mention the pre-2008 ones such as cryptographic hashing, SQL CLR and many more. In performance terms, these are great enhancements.

The one exception is Transparent Data Encryption, where the whole database is encrypted. This can considerably reduce performance if the SQL Server box is not sufficiently powerful. It this is the case, it is a good time to offload all the encryption and decryption to third-party hardware. SQL Server allows third-party management of encryption and decryption through Extensible Key Management.

Extending the earlier courier analogy, consider the fact that even if our letter is secure and safe in our hands, as soon as we hand it to the courier it is exposed to risk and can be compromised. SQL Server 2008 has many new features, which secure data while it is being communicated between applications. A number of features were introduced that check whether data is manipulated during transmission.

Data is everywhere and taking in terms of Terra Bytes (TB) is the current reality. When a large amount of data needs to be handled, there are two major challenges. The first challenge is the actual encryption process and the resources needed to perform it. The second challenge is how to use the data once it has been encrypted.  In a regular database searching through TBs of data can take a very long time. Imagine how long this could take in and encrypted database?

In Seattle, Michael and I discussed these challenges and a few more subjects. The discussion lasted more than four hours. I have always known Michael to be an excellent author. He is renowned in the industry for his expertise of XML and Full Text Search. To my mind, he is an expert who has the extraordinary ability of relating complex concepts in simple terms. No matter how long, boring or complicated the topic, his delivery is always sweet, like chocolate that melts in the mouth.

Michael always addresses uncommon subjects. Perhaps his experience as a Sergeant in the army has given him the spirit to explore the unexplored.  I have never before encountered a single book on the subject of encryption for SQL Server and Michael’s will a “first”.

I recently had the pleasure of reading it and especially like the manner in which he and his co-author, Rodney, explain the significance of encryption. While many of the concepts covered are domain-specific, quite a few topics are common to all and the appendix is a “must read” for anyone planning a security strategy. One thing that really makes this book special is the fact that each module is written independently and you can find solutions by simply reading the relevant one.

I am a hands-on developer and only like books that have a lot of workable examples. With the exception of the first chapter, the book is filled with examples and hands-on experiments. The first chapter in itself is quite unique, as it not only provides a introduction to encryption, but also the very interesting history of encryption.  Even non-technical readers will enjoy this.

Summary:
It is my great pleasure to welcome this one-of-a- kind book to the SQL Server world. There is no doubt that this book is exceptional and will inspire anyone one who is ready to take their current security mechanism to the next level using encryption.

Stars : 5 Stars

Reference: Pinal Dave (http://blog.sqlauthority.com)

DBCC (Database consistency checker) are used to check the consistency of the databases. The DBCC commands are most useful for performance and trouble shooting exercises.

I have listed down and explained all the DBCC commands available in SQL Server 2005, with examples.

The DBCC Commands broadly falls into four categories:

• Maintenance
• Informational
• Validation
• Miscellaneous

Maintenance Commands

Performs maintenance tasks on a database, index, or filegroup.

1. CLEANTABLE – Reclaims space from the dropped variable-length columns in tables or index views.

2. DBREINDEX – Builds one or more indexes for the table in the specified database. (Will be removed in the future version, use ALTER INDEX instead)

3. DROPCLEANBUFFERS – Removes all clean buffers from buffer pool.

4. FREEPROCCACHE – Removes all elements from the procedure cache

5. INDEXDEFRAG – Defragments indexes of the specified table or view.

6. SHRINKDATABASE – Shrinks the size of the data and log files in the specified database

7. SHRINKFILE – Shrinks the size of the specified data or log file for the current database or empties a file by moving the data from the specified file to other files in the same filegroup, allowing the file to be removed from the database.

8. UPDATEUSAGE – Reports and corrects pages and row count inaccuracies in the catalog views.

Informational Commands

Performs tasks that gather and display various types of information.

1. CONCURRENCYVIOLATION – is maintained for backward compatibility. It runs but returns no data.

2. INPUTBUFFER – Displays the last statement sent from a client to an instance of Microsoft SQL Server 2005.

3. OPENTRAN – Displays information about the oldest active transaction and the oldest distributed and nondistributed replicated transactions, if any, within the specified database.

4. OUTPUTBUFFER – Returns the current output buffer in hexadecimal and ASCII format for the specified session_id.

5. PROCCACHE – Displays information in a table format about the procedure cache.

6. SHOW_STATISTICS – Displays the current distribution statistics for the specified target on the specified table

7. SHOWCONTIG – Displays fragmentation information for the data and indexes of the specified table or view.

8. SQLPERF – Provides transaction log space usage statistics for all databases. It can also be used to reset wait and latch statistics.

9. TRACESTATUS – Displays the status of trace flags.

10. USEROPTIONS – Returns the SET options active (set) for the current connection.

Validation Commands

Performs validation operations on a database, table, index, catalog, filegroup, or allocation of database pages.

1. CHECKALLOC – Checks the consistency of disk space allocation structures for a specified database.

2. CHECKCATALOG – Checks for catalog consistency within the specified database.

3. CHECKCONSTRAINTS – Checks the integrity of a specified constraint or all constraints on a specified table in the current database.

4. CHECKDB – Checks the logical and physical integrity of all the objects in the specified database.

5. CHECKFILEGROUP – Checks the allocation and structural integrity of all tables and indexed views in the specified filegroup of the current database.

6. CHECKIDENT – Checks the current identity value for the specified table and, if it is needed, changes the identity value.

7. CHECKTABLE – Checks the integrity of all the pages and structures that make up the table or indexed view.

Miscellaneous Commands

Performs miscellaneous tasks such as enabling trace flags or removing a DLL from memory.

1. dllname (FREE) – Unloads the specified extended stored procedure DLL from memory.

2. TRACEOFF – Disables the specified trace flags.

3. HELP – Returns syntax information for the specified DBCC command.

4. TRACEON – Enables the specified trace flags.

Good Luck!

Quarta-feira, 18 de Novembro de 2009, 23h13

“Se não está doendo agora, não deve doer depois. Pode colocar” . Agora posso dizer que dói. E é uma dor irritante, e expansiva, literalmente. Estou falando desses elásticos em minha boca. Oito. Cor verde-água. Parece que em dois dias para de doer, aí vem a aparelhagem definitiva. Bem que a dentista disse que, perguntando pra quem já colocou aparelho, o que ele mais se lembra é desses elásticos.

Bom, provinha bem fácil de português hoje. Quer dizer, era pra ser difícil, mas a professora facilitou nossa vida.

Aquela senhora tem um piano
Que é agradável mas não é o correr dos rios
Nem o murmúrio que as árvores fazem…

Para que é preciso ter um piano?
O melhor é ter ouvidos
E amar a Natureza.

- Alberto Caeiro, heterônimo de Fernando Pessoa em “O Guardador de Rebanhos” (^)
“Lindo!” – BORGES, Susi M. K. S.

Apesar de tudo, eu ri de muitos fatos que aconteceram hoje. O principal deles, eu mexendo em um servidor na escola com conta de administrador. Por conexão remota, eu loguei naquela servidor, arrumei umas coisas e outras, e vi que um serviço não estava funcionando. Como ele dependia da rede, eu simplesmente desabilitei o adaptador de rede. Cheguei no T.I.: “moço, a gente tava usando o servidor, mas ele caiu do nada e não volta mais..“. hsuahsaushauhsa

Outra coisa engraçadíssima foi a discussão do Andrey com a Juh, (…).

23h29

There five type of constrains provided by SQL Server. We shall see each one of then in details

1. Primary Key Constraint

A primary key is used to uniquely identify each row in a table. A primary key can consist of one or more then more columns in table. When they consist of more then one column they are called composite key. It ensures unique non-null key.

CREATE TABLE Student(
StudID INT PRIMARY KEY,
StudName VARCHAR(50)
)

or

ALTER TABLE Department ADD PRIMARY KEY (DeptID)

2. Foreign Key Constraint

A foreign key is a field in a table that matches the primary key column of another table. It establishes and enforces a link between data of two tables. It ensures that value points to a valid key.

CREATE TABLE Subjects(
SubID INT,
SubName VARCHAR(50),
StudID INT FOREIGN KEY REFERENCES Student(StudID),
TotalMarks INT,
)

or

ALTER TABLE Subjects(ADD CONSTRAINT StudID_Fk
FOREIGN KEY (StudID) REFERENCES Student(StudID)

3. Unique Constraint

It is similar to Primary Key Constraint. It ensures that every value in the column is unique value. It allows one NULL value.

CREATE TABLE Employee(
EmpID INT,
FirstName VARCHAR(50),
LastName VARCHAR(50),
DeptID INT,
Salary INT,
ProjectCode INT UNIQUE,
)

or

ALTER TABLE Employee ADD UNIQUE (ProjectCode)

4. Nullability Constraint

It defines whether a column will accept a NULL value or not. It is referred to as nullability of the column.

CREATE TABLE Employee(
EmpID INT,
FirstName VARCHAR(50) NOT NULL,
LastName VARCHAR(50),
DeptID INT,
Salary INT,
ProjectCode INT
)

or

ALTER TABLE Employee ALTER COLUMN FirstName VARCHAR(50) NOT NULL;

5. Check Constraint

Check Constraint is extensively used to enforcement of general data-validation rules or simple business rules. Such as correct date range, max value that can be inserted into a table, etc.

CREATE TABLE Employee(
EmpID INT,
FirstName VARCHAR(50),
LastName VARCHAR(50),
DeptID INT,
Salary INT,
ProjectCode INT,
CONSTRAINT chk_sal CHECK (Salary BETWEEN 1000 AND 25000)
)

or

ALTER TABLE Employee
ADD CONSTRAINT chk_salary CHECK (Salary BETWEEN 1000 AND 25000)

Now in the below example show the all the Constraints in one table,

CREATE TABLE Employee(
EmpID INT PRIMARY KEY,
FirstName VARCHAR(50) NOT NULL,
LastName VARCHAR(50),
DeptID INT FOREIGN KEY REFERENCES Department(DeptID),
Salary INT,
ProjectCode INT UNIQUE,
CONSTRAINT chk_salary CHECK (Salary BETWEEN 1000 AND 25000)
)

It is very easy to find out some basic details of any table using the following Stored Procedure.

USE AdventureWorks
GO
EXEC sp_spaceused [HumanResources.Shift]
GO

Above query will return following resultset

The above SP provides basic details such as rows, data size in table, and Index size of all the indexes on the table.

If we look at this carefully, a total of three indexes can be found on the table HumanResources.Shift.

USE AdventureWorks
GO
SELECT *
FROM sys.indexes
WHERE OBJECT_ID = OBJECT_ID('HumanResources.Shift')
GO

The above query will give result with query listing all the index on the table.

There is a small puzzle for all of you here. The puzzle is to write a query that will return the size for each index that is listed in above query. We need a query that will return an additional column in the above listed query and it should contain the size of the index. In our case, we will have three different sizes, which should add up to a total of 40 KB as shown in earlier query, where the total size is displayed.

I will publish the solution with due credit on this blog.

Reference: Pinal Dave (http://blog.sqlauthority.com)

Update: Do not forget to checkout last three photos and follow me on twitter (of course!)

I have previously documented my four-day experience of SQL PASS 2009 Summit at Seattle. There were many reasons for SQL enthusiasts to attend the SQL PASS event; I am listing my own reasons here in order of importance to me.

• Networking with SQL fellows and experts
• Putting face to the name or avatar
• Learning and improving my SQL skills
• Understanding the structure of the largest SQL Server Professional Association
• Attending my favorite training sessions

During these four days, there was so much happening that it is difficult to document everything. I had tried to cover this event briefly on a daily basis in the following blog posts:

SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 1
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 2
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 3
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 4

I will list a few of the additional details that I have not included in the earlier post. Keynotes were the best part of the event, and I have covered major points of the keynote in above mentioned posts. I had met many SQL Legends during this event and included information regarding them. However, there were few things I still missed and I am listing them here. Seattle is great city, and I am visiting it the second time. This time I got an opportunity to take the Underground city tour and I had really enjoyed.

It was great to meet SQL Server MVP Glenn Berry at the MVP Summit. He is a very kind and friendly person. You will always find him hanging around with people from different organizations and countries. If you try to eavesdrop his conversation, you will hear terms like ‘dmv’, ‘performance’, and ‘optimized query’ very often. He is very much known for his excellent optimization script known as “SQL Server 2008 Diagnostic Information Queries“. If you have never taken a look at that, I urge you to go there and check this out. I believe that even if he blogs once a year only with this script, his fans will not complain. I have previously published his interview on my blog. Please note that he is the only person ever featured in an interview on this blog.

It depends! This is one most loved (or hated) phrase in the world of programmers or DBA. It is quite common to start answering question using this phrase. Mostly, this phrase initiates humor but rarely, people take this as offence. Again the intent of speaker is not always conveyed properly, it depends on how the phrase is used (I could not resist to use this phrase as well ). I had very interesting discussion with Michelle Ufford and Jason Strate when we were waiting for coffee at one afternoon. We discussed both the sides of this phrase. Michelle suggested many good points when and why this phrase is valid. Jason also suggested that this phrase is commonly used a) when the presenter does not have sufficient information to answer or b) when the presenter does not know the answer. We discussed that it would be really interesting to start the conversation answering the most possible answer and then talking about special cases (for which it depends is quite commonly used.) Let us see one example.

Q: Does index improve performance?
A1: It depends on query and data you have.
A2: Usually YES; however, there are cases when it reduces performance, for which the query and data needs to be examined carefully.

There are times when it depends totally make sense. I use it several times; I love the blog of Andy Warren which talks is branded as it depends. This discussion between three of us was just a friendly discussion, and if you think we are talking about you, it is wrong!

During this event, I had great conversation with SQL Legend Buck Woody. This man is full of energy and may be the most loved person in this summit. His session was the funniest session I have ever attended. At the end of his session, I had more than 2 pages of my notebook filled with notes. If I have wrote down how many times, I have laughed loudly, I would have no time to do anything else. Buck had a good hour of discussion with me. We discussed many different topics, ranging from Community to Microsoft and Collage Students to SQL. I am very thankful to Buck for spending his valuable time with me – I am honored.

Joe Celko – this name is very popular in SQL world, and I admit that I was always afraid of him. Every time I see his photo, I just felt nervous. I never thought that I should meet him. Honestly, for the same reason, I did not attend his session. I was absolutely wrong. I met him right after his session was over. He is one of the most friendly people I have met in my life. He is very soft spoken. He gauges the level and understanding of other person and speaks at the same level. He made me laugh and taught many good techniques for how to become good speaker and presenter. When I said I was sorry that I was scared of him, he laughed and said that he knows this. Boy, what a mistake I did!! I should have attended his session. Well, at least I am accepting my mistake here. He is indeed a very friendly soul. He promised me that one time he will come to India.

Brian Moran is the newly elected board member; I would like to call him as ‘the Man with 1000 successful ideas‘. You have to come across him to know what I am talking about. I had the great opportunity to meet him and discuss few things, besides SQL. Brian had many excellent ideas about how to build the community, how to help SQL PASS and few excellent ideas about how to take PASS to the next level. I am glad that he is one of the board members for PASS. PASS is all about passion, and Brian clearly demonstrates the same.

I met all of them and had a great conversation with them. It was great to meet Ed Hackney; he is a wonderful person and very easily approachable. He talked about SQL community in India and how any community cannot be restrained within geographical boundaries.

I was waiting to meet Thomas LaRock. He is an excellent SQL Master, and he talked in detail about outsourcing SQL technology and SQL community. I really enjoyed meeting him and spending some time with him during the summit. I plan to learn more from him when I meet him next time.

Robert Cain, he is one of the very few SQL masters, who have expertise in .net and Business Intelligence at the same time. I have previously wrote about him in Big Thinkers – Robert Cain. He has given approval that I can write about his BI presentation on this blog. I will write about it soon.

I have previously written a lot about Greg Low on this blog. However, I just can not resist to put this excellent photo once again here. He has great respect for the international community; and he had spent some quality time with me discussing how to enhance and grow the global community. Greg gave his insight and few plan cache tips as well. You can read my review of his book ‘Book Review – The Rational Guide to Building Technical User Communities (Rational Guides)‘. You can also read our discussion on plan cache ‘SQL SERVER – Plan Caching and Schema Change – An Interesting Observation‘.

Following image is for sure very interesting! Can you recognize the person? Well, just go here and read about Mr. Denny. And I do have permission from him to publish this photo!

PASS 2010 dates are announced; this event will take place between 8 and 12 November 2010.

Following image is my favorite as it brings the future and past of PASS together. Kevin Kline, a hero of PASS summit, (as he dedicated 10 years of his life to serve PASS board) is in same frame with Rushabh Mehta, who is President Elect for 2010.

Now I am coming to the most interesting part of my experience. I want to introduce to all of you the youngest SQL PASS fan and follower. Her name is Shaivi Dave, and she is big fan of SQL PASS! Shaivi suggests that save your money and register right away for PASS. There is no other conference which is as valuable as SQL PASS.

She had conveyed her wish to SQL PASS President Elect Rushabh Mehta when she was just 19 days old. May be one of following years, we will see her at summit.

This is note is addendum to my four original posts. I strongly suggest you all to read my earlier posts for details on keynote and other SQL legends.

SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 1
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 2
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 3
SQLAuthority News – SQL PASS Summit, Seattle 2009 – Day 4

If you have visited this event and have something more to add to what I have written, please feel free to add it here as a comment. I am looking forward for you all to add more details and information here. Follow me on twitter.

Reference: Pinal Dave (http://blog.SQLAuthority.com)

I am building a web app with Ben Alabaster, and one of the requirements is for the user to be able to flag items for moderators. So the user can flag entity A, entity B, entity C, etc…

So I created a single flag table.

Flag Table

Which I then tried to tie it to the entity tables, hoping for something like

Ideal Foriegn Key Relationships

Where all the foreign key relationships were from [flag].[entity_id] to [EntityX].[id]

Then when I wanted the top 10 flags from a particular entity (B in this case), I could run a query like

Unfortunately, if you were to create the above table relationship, and run the following inserts

The following statement

would fail as expected, as expected, with the following error. “The INSERT statement conflicted with the FOREIGN KEY constraint “FK_flag_EntityA”. The conflict occurred in database “test”, table “dbo.EntityA”, column ‘id’.”

But

would also fail, which was undesired, with the following error: “The INSERT statement conflicted with the FOREIGN KEY constraint “FK_flag_EntityB”. The conflict occurred in database “test”, table “dbo.EntityB”, column ‘id’.” +

So, my options with regards to referential integrity are :

1. Ditch the referential integrity, which I am vehemently opposed to. ++
2. Create multiple flag tables, each with the exact same schema, but a different Foreign Key relationship, which just seems wrong.
3. Managing referential integrity via triggers.

While I’m not a big fan of triggers, the ‘Managing referential integrity via triggers.’ option seems like the only tolerable one. So I added the [entity_type] column to my flag table.

Flag Table With Entity Type

Removed the relationships

No Relationships

And wrote the following trigger to manage the foreign key relationship.

Now, when you run

The trigger doesn’t find a match in the appropriate table, rolls back the insert, and gives you a descriptive error message.

Unable to find foriegn key match on entity type ‘B’, id ‘5′.

However, a good value is accepted.

I’m still not happy with this approach, but it does seem to be the lesser of all the evils. Please let me know with a comment if there is another option I’ve overlooked. Thanks.

* Frankly I was surprised it even compiled.
+ Unless of course you were unfortunate enough to test this in a coincidental situation where all tables happened to contain the id of every test you ran.
++ Yes ‘vehemently’

EDIT (11/10/2009) : It just occurred to me that this article does not take into account what would happen if the entity tables were to delete a row which this table was pointing to. When I designed my tables this was taken into account, but since we are not planning to allow actual deletions, it was left out. However, if you were to implement this strategy, where entities could be deleted, a delete trigger would need to be created for each entity table.

System Stored Procedure Script

Have you seen script of System Stored Procedure of SQL Server? Well if you are curious creature like me, then why not see it.

To do that, we need to use another System Stored Procedure sp_helptext. It will display the script behind the specified System Stored Procedure.

Syntax:

Example:

Go ahead and try it with other System Stored Procedures.

Did you see how Microsoft codes their Stored Procedures? If you think “Even I can do this stuff“, feel luck and please forward your resume to Microsoft Corporation!

Good Luck!

SERVERPROPERTY Function

How does one get list all Server Properties? Well, we can use a very helpful system function SERVERPROPERTY. It will return information about the server instance for a specified property.

Syntax:

SERVERPROPERTY (propertyname)

I have kept the following script in my archives, you may do the same.

If you want to check what all these different Server Property means, please also see http://msdn.microsoft.com/en-us/library/ms174396.aspx

Good Luck!

Recently, a colleague and I found ourselves in the situation of needing to concatenate values from multiple rows of a MS SqlServer database table. We were trying to form a comma-delimited list of phone numbers for every customer in our database. One customer may have many phone numbers. Here is a simplified diagram visualizing the relationship between customer and phone numbers:

Customer - Phone Number Relationship

The format of data we were looking for was:

We tried various queries to perform the concatenation correctly but none of our solutions seemed to do the job perfectly; either the final ‘PhoneNumbers’ string would have an additional comma at the end or some other undesired effect. We finally came across an article explaining in great detail of how to use TSQL (the SQL engine behind SqlServer) to perform the operations we needed.

http://www.projectdmx.com/tsql/rowconcatenate.aspx

This article has various examples describing AND explaining how to do multiple row value concatenations such as explicit examples for “Concatenating values when the number of items is small and known upfront” and “Concatenating values when the number of items is not known”. The author even walks through a recursive solution or two.

We determined that we knew none of our customers had more than five phone numbers based on the fact that they were limited to the PhoneType enumeration which only has five values. This allowed us to use the articles first example to get our job done efficiently. Here is our final solution:

SELECT CustomertId, REPLACE(
 '"' + MAX( CASE seq WHEN 1 THEN phoneNumber ELSE '' END ) + '",' +
 '"' + MAX( CASE seq WHEN 2 THEN phoneNumber ELSE '' END ) + '",' +
 '"' + MAX( CASE seq WHEN 3 THEN phoneNumber ELSE '' END ) + '",' +
 '"' + MAX( CASE seq WHEN 4 THEN phoneNumber ELSE '' END ) + '",' +
 '"' + MAX( CASE seq WHEN 5 THEN phoneNumber ELSE '' END ) + '"', ',""', '' ) as PhoneNumbers
FROM (
 SELECT pn1.CustomerId, pn1.PhoneNumber, (
 SELECT COUNT(*)
 FROM PhoneNumber pn2
 WHERE pn2.CustomerId = pn1.CustomerId
 AND pn2.phoneNumber <= pn1.phoneNumber)
 FROM PhoneNumber pn1) PhoneNumbersPerParty ( CustomerId, phoneNumber, seq )
GROUP BY CustomerId
By: Jesse Webb

For SQL Server, sp_depends is the recommended method, as the supporting system tables will be automatically selected based on the version.

In Oracle, the string operations are case sensitive. so before you start smashing your head to the desk, change the case and try to find the objects.

List all Foreign Key Constraints of Database or Table

How often we face this problem? The Foreign Key constraint of the table preventing us from deleting or modifying records.

To deal with them, first we need to have information about these constraints. How nice it would it be to get details of all the Foreign Key constraint defined in the Database or on a Table.

Good News, yes we can. Just use following script:

See also:

SQL Server – List all Constraints of Database or Table

SQL Server – Drop All Table Constraints

Good Luck!

Drop All Table Constraints

You want to redefine all the constraints set on a Table. To do that you need to first drop all the existing constraints set on the table. Following is the simple script to do so the same:

The above script does not drop DEFAULT constraint set on the Table.

See also:

SQL Server – List all Constraints of Database or Table

SQL Server – List all Foreign Key Constraints of Database or Table

Good Luck!

List all Constraints of Database or Table

Many times when we are using DML commands like: INSERT, UPDATE, DELETE, we get errors because one or the other constraint is set on the table. It get really annoying when we are new to a Database and don’t know what constraints are set on the tables.

It would be of great help if we get the list of all the constraints in the database. Below are two methods to do the same.

Method 1

Use sys.objects to get the constraint information.

The above query will display all the fields of sys.objects. We can refine the above query to display the result more tasteful.

Method 2

Use INFORMATION_SCHEMA.TABLE_CONSTRAINTS to get the constraint information. This query has one shortcoming; it won’t display DEFAULT constraints of the database

To display DEFAULT constraints in the database we can use following SQL Statement.

See also:

SQL Server – Drop All Table Constraints

SQL Server – Stored Procedure to Drop All Database Constraints

Good Luck!

Find Nth Highest or Lowest Value in Table

This one is a tricky question. We all assume that this is not a big deal, but when this question is asked in the interviews, we try all the permutations and combinations of SELECT statements, but are never close to the answer.

There are many solutions to this problem. I have listed down some of the simple methods to find out Nth highest and Nth Lowest values in the table.

Method 1

Method 2

Method 3

Method 4

Method 5

Method 6

Hope you find this useful.

Good Luck!

Convert.ToDateTime(date1).ToString(“dd-MMM-yyyy”);

—–

declare @myxml xml;

select @myxml = ‘<ParameterValues>

<ParameterValue>
<Name>TO</Name>
<Value>myemail@mail.com</Value>
</ParameterValue>

<ParameterValue>
<Name>BCC</Name>
<Value>myemail@mail.com</Value>
</ParameterValue>

<ParameterValue>
<Name>IncludeReport</Name>
<Value>True</Value>
</ParameterValue>

<ParameterValue>
<Name>Subject</Name>
<Value>Customers in Switaly</Value>
</ParameterValue>

</ParameterValues>’

–select @myxml

–select @myxml.query(‘/ParameterValues/ParameterValue/Value[../Name = ''Subject'']‘)
select @myxml.query(‘/ParameterValues/ParameterValue/Value12′)

=======================

select * from wsiagingreport
select [XmlQuerySql].value(‘(/ROOT/Slot1/SlotPeriodValue)[1]‘, ‘varchar(200)’) as Slot1PeriodValue,
[XmlQuerySql].value(‘(/ROOT/Slot1/SlotPeriodType)[1]‘, ‘varchar(200)’) as SlotPeriodType,
[XmlQuerySql].value(‘(/ROOT/Slot1/ThresholdType)[1]‘, ‘varchar(200)’) as ThresholdType,
[XmlQuerySql].value(‘(/ROOT/Slot1/ThresholdValue)[1]‘, ‘varchar(200)’) as ThresholdValue
from wsiagingreport

====================================

Except in sqlserver is equivalent to Minus in ORACLE

===

usage of case when then else end
………………………….
select @Slot1_Count = count(*) from wsiincident
where @Slot1_PeriodValue >=
case when @Slot1_PeriodType =’Hour’
     then datediff(hour, sourcetoolcreateddate,getdate())  
     when @Slot1_PeriodType =’Day’
     then datediff(Day, sourcetoolcreateddate,getdate())
     when @Slot1_PeriodType =’Week’
     then datediff(Week, sourcetoolcreateddate,getdate())
     when @Slot1_PeriodType =’Fortnight’
     then datediff(Day, sourcetoolcreateddate,getdate())/14
     when @Slot1_PeriodType =’Month’
     then datediff(Month, sourcetoolcreateddate,getdate())
     when @Slot1_PeriodType =’Quarter’
     then datediff(Quarter, sourcetoolcreateddate,getdate())
     when  @Slot1_PeriodType =’Year’
     then datediff(Year, sourcetoolcreateddate,getdate())
     else 0 end

===================================

select datediff(Year,’2003-12-12′,getdate())
declare @ss nvarchar(100)
set @ss = ‘h’
select case when @ss =’h’ then datediff(hour,’2003-12-12′,getdate())
   when @ss =’m’ then datediff(minute,’2003-12-12′,getdate())
   when @ss =’s’ then datediff(second,’2003-12-12′,getdate())
   else 0 end

============================================
suppose in a sp u need like this

create proc p_c
as
begin
select * from table
where names in (’s,g,d’)
end  .. this will work

but
create proc p_c
@strings nvarchar(1000)
as
begin
select * from table
where names in (@strings )
end  .. this wont work as strings is a parameter.

To solve this problem
create a splitstring function and split the string and insert into a temporary table

create proc p_c
@strings nvarchar(1000)
as
begin
select * from table
where names in (select names from db0.splitstrings(@strings))
end  .. this will work
splitstring function is:
ALTER FUNCTION [dbo].[SplitStrings](@String varchar(8000), @Delimiter char(1))       

      returns @temptable TABLE (items varchar(8000))       

as       

begin       

    declare @idx int       

    declare @slice varchar(8000)       

    select @idx = 1       

        if len(@String)<1 or @String is null  return       

    while @idx!= 0       

    begin       

        set @idx = charindex(@Delimiter,@String)       

        if @idx!=0       

            set @slice = left(@String,@idx – 1)       

        else       

            set @slice = @String       

        if(len(@slice)>0)  

            insert into @temptable(Items) values(@slice)       

        set @String = right(@String,len(@String) – @idx)       

        if len(@String) = 0 break       

    end   

return       

end 

usage : where id in (select id from [SplitStrings](‘a,b’,',’))
===================================

How to Handle Single Quote in String

This is the common one-time problem (not for all ) faced by a new DBA Developer, and even I did.

The solution to this problem is rather simple. Use an extra single quote, with the quote character occurring in the string.

See the example below:

Error Message

See also:

Function to split comma delimited String or List

How to handle single quote in sqlquery string?

Good Luck!

The Professional Association for SQL Server (PASS) is an independent, not-for-profit association, dedicated to supporting, educating, and promoting the Microsoft SQL Server community. From local user groups and special interest groups (Virtual Chapters) to webcasts and the annual PASS Community Summit – the largest gathering of SQL Server professionals in the world – PASS is dedicated to helping its members Connect, Share, and Learn.

Today was a big day as PASS announced the executive board members for the term starting on Jan 1, 2010. I would like to express my congratulations to all new executives of PASS. Please read official press note here.

The newly elected board members at executive positions are as following:

• Rushabh Mehta – President
• Bill Graziano – Executive Vice President, Finance
• Rick Heiges – Vice President, Marketing

A little bit more details about executives.

Rushabh Mehta is a Mentor for Solid Quality Mentors’ global Business Intelligence Division and the Managing Director for Solid Quality India. Rushabh has worked with Microsoft SQL Server since 1998 and has designed and developed BI systems on the Microsoft platform since 2001, including a predictive analysis system, a health-care analysis solution, and a multi-terabyte financial decision support system. He has been the lead architect for many large-scale and complex BI solutions for clients such as Publix, Raymond James Financial, Jackson Hewitt, and Checkers. Rushabh has been an active volunteer with PASS since 2000 and has also served on the board  for a number of years. Rushabh is also a SQL Server MVP and a frequent speaker at large conferences and PASS Chapters around the world.

Bill Graziano is an active member of PASS since 2001, Bill currently serves on the Board of Directors, where he is responsible for the overall marketing for PASS and PASS Summit. Bill co-founded SQLTeam.com, a web site for SQL Server developers and database administrators. In addition to managing the site, he writes articles and helps users with their most vexing problems. An involved participant in the SQL Server community for seven years, Bill was recognized as a SQL Server MVP in 2004 and still holds that designation.

Rick Heiges is a Sr. Solutions Consultant with Scalability Experts working with customers on solutions within the SQL Server environment and educating users on SQL Server 2005 by speaking at user groups, conferences, labs, and road shows across the USA, Europe, and Africa. He holds an MBA and a M.S. in MIS as well as a B.S. in Computer Science. In addition, he also has attained MCTS:SQL2005 and MCITP:DBA certifications.

Not only are these three executives experts in their domain, but have been friends for many years. Here are few of their photos from their activities at old PASS events.

Many congratulations to all of you. SQL Server community has lots of expectation from you and we are confident that you will not only satisfy them but will go way beyond our imaginations.

Reference: Pinal Dave (http://blog.SQLAuthority.com)

Image courtesy: Rick Heiges, Rushabh Mehta, SQL PASS

]]> http://bhaveshgpatel.wordpress.com/2009/10/29/sql-server-set-functions-count-max-min-sum-and-avg/ Thu, 29 Oct 2009 14:51:16 +0000 Bhavesh Patel http://bhaveshgpatel.wordpress.com/2009/10/29/sql-server-set-functions-count-max-min-sum-and-avg/

Set Functions – COUNT, MAX, MIN, SUM and AVG

Many times the information we require from table doesn’t relate to individual rows but to set of rows. In such case we can use Set functions provided by the SQL Server. These function are COUNT, MAX, MIN, SUM and AVG. Set functions operate on groups of rows.

1. COUNT

The COUNT function returns the rows count in the table.  When used with WHERE clause, only number of rows which satisfy the condition will be returned. The DISTINCT can be used to get the count of rows with unique values.

Example

2. MAX

The MAX function returns the maximum value in the specified column. The MAX function can also be used as the part of sub-query.

Example

3. MIN

The MIN function returns the minimum value in the specified column. The MIN function can also be used as the part of sub-query.

Example

4. SUM

The SUM function adds up the values in a specified column. The column must be of one of numeric data types. The DISTINCT can be used to get the sum of only unique values.

Example

5. AVG

The AVG function returns the average of all the values in the specified column. As with SUM function, the column must be of one of numeric data types. The DISTINCT can be used to get the average of only unique values.

Example

Good Luck!