We often need to find the last running query or based on SPID need to know which query was executed. SPID is returns sessions ID of the current user process. The acronym SPID comes from the name of its earlier version, Server Process ID.

To know which sessions are running currently, run the following command:

SELECT @@SPID
GO

In our case, we got SPID 57, which means the session that is running this command has ID of 57.

Now, let us open another session and run the same command. Here we get different IDs for different sessions.

In our case, we got SPID 61. Please note here that this ID may or may not be sequential.

In session with SPID 61, we will run any query. In session with SPID 57, we will see which query was run in session with SPID 61.

Let us run a simple SELECT statement in session with SPID 61 and in session with SPID 57 run the following command.

DBCC INPUTBUFFER(61)
GO

Now, here in DBCC command we have passed the SPID of previous session; we will see the text below. The following image illustrates that we get the latest run query in our input buffer.

There are several ways to find out what is the latest run query from system table sys.sysprocesses.

DECLARE @sqltext VARBINARY(128)
SELECT @sqltext = sql_handle
FROM sys.sysprocesses
WHERE spid = 61
SELECT TEXT
FROM sys.dm_exec_sql_text(@sqltext)
GO


The following image portrays that we get the latest run query in our input buffer.

Please note that in any session there may be multiple running queries, but the buffer only saves the last query and that is what we will be able to retrieve.

There is one more way to achieve the same thing – using function fn_get_sql

DECLARE @sqltext VARBINARY(128)
SELECT @sqltext = sql_handle
FROM sys.sysprocesses
WHERE spid = 61
SELECT TEXT
FROM ::fn_get_sql(@sqltext)
GO

All the three methods are same but I always prefer method 2 where I have used sys.sysprocesses.

Today, we have explored a very simple topic. Let me know if you find it useful.

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

Some time ago I was helping one of my Junior Developers who presented me with an interesting situation. He had a table with Identity Column. Because of some reasons he was compelled to delete few rows from the table. On inserting new rows in the table he noticed that the rows started from the next identity value which created gap in the identity value. His application required all the identities to be in sequence, so this was certainly not a small issue for him.

The solution to this issue regarding gap in identity column is very simple. Let us first take a look at his application’s situation wherein there is missing identity and then we will move on to the solution.

Developers can easily deter the above issue by avoiding gap in sequence of identity column through two additional SQL Tricks of reseeding identity.

We will now see the same example with the solution to the above gap issue. On deleting records, table was reseeded with identity, which was deleted. Download complete SQL Script here.

USE AdventureWorks
GO
/* Create a table with one identity column */
CREATE TABLE TableID (ID INT IDENTITY(1,1), Col VARCHAR(10))
GO
/* Insert 10 records with first value */
INSERT INTO TableID (Col)
VALUES ('First')
GO 10
/* Check the records in table */
SELECT *
FROM TableID
GO
/* Delete last few records */
DELETE
FROM TableID
WHERE ID IN (8,9,10)
GO
/* Check the records in table */
SELECT *
FROM TableID
GO
/* Get current Max Value and reseed table */
DECLARE @MaxID INT
SELECT @MaxID = MAX(ID)
FROM TableID
DBCC CHECKIDENT('TableID', RESEED, @MaxID)
GO
/* Insert 10 records with second value */
INSERT INTO TableID (Col)
VALUES ('Second')
GO 5
/* Check the records in table */
SELECT *
FROM TableID
GO
/* Clean Database */
DROP TABLE TableID
GO


I hope is solution is clear to all my readers and they will use it to avoid problems related to gap in identity column. Do send me your feedback on this article and let me know if you all need further explanation.

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

Just a day ago I have received following email from Siddhi and I found it interesting so I am sharing with all of you.

Just another day I was playing with my query which I posted earlier SQL SERVER – 2008 – 2005 – Find Longest Running Query – TSQL and I found that I got error devide by zero. I have fixed this error in following query as well I have updated query to return time in millisecond instead of microsecond. Jerry Hung has also posted similar solution in comments of original article.

I strongly suggest to read original article to now more about introduction and learn about DBCC command which clears cache.

SELECT DISTINCT TOP 10
t.TEXT QueryName,
s.execution_count AS ExecutionCount,
s.max_elapsed_time AS MaxElapsedTime,
ISNULL(s.total_elapsed_time / 1000 / NULLIF(s.execution_count, 0), 0) AS AvgElapsedTime,
s.creation_time AS LogCreatedOn,
ISNULL(s.execution_count / 1000 / NULLIF(DATEDIFF(s, s.creation_time, GETDATE()), 0), 0) AS FrequencyPerSec
FROM sys.dm_exec_query_stats s
CROSS APPLY sys.dm_exec_sql_text( s.sql_handle ) t
ORDER BY s.max_elapsed_time DESC, ExecutionCount DESC,
GO

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

Previously I posted SQL SERVER – Find Row Count in Table – Find Largest Table in Database – T-SQL. Today we will look into the same issue but with some additional interesting detail.
We can find the row count using another system SP sp_spaceused. This SP gives additional information regarding disk space reserved on database as well. Well, when I ran the SP on AdventureWorks first time, I suspected that database SP is not providing me correct results.

After a bit investigating I found that it may be possible that due to any reason may be the usage on AdventureWorks database might not be updated. I ran same SP with additional param as shown below and it provided me updated information for the same. Once I ran the SP with @updateusage param, it updated the status of the database. When I ran it again next time without param it gave the same results.

The reason for above behavior is when dellocation of space happened in database (e.g. dropping table or truncating table) it does not release the used space right away. However, when @updateusage param is used database engine scans whole database and update the sapce usage in respective tables.
Let me know if you guys have any interesting observation like this.

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

UPDATE : Updated this query with bug fixed with one more enhancement SERVER – 2008 – 2005 – Find Longest Running Query – TSQL – Part 2.

Recently my company owner asked me to find which query is running longest. It was very interesting that I was not able to find any T-SQL script online which can give me this data directly. Finally, I wrote down very quick script which gives me T-SQL which has ran on server along with average time and maximum time of that T-SQL execution. As I keep on writing I needed to know when exactly logging was started for the same T-SQL so I had added Logging start time in the query as well.

The reason I started to use this script to find out longest running query as if query is changed a bit it will display it as new row and new log start time. This way when I am improving T-SQL query or Stored Procedure I can check their progress in the query and does not have to get bothered with previous data.

I always run following DBCC command before I started to use my query. Following DBCC commands clears the cache of the server and starts fresh logging of the query running time.

DBCC FREEPROCCACHE

Run following query to find longest running query using T-SQL.

SELECT DISTINCT TOP 10
t.TEXT QueryName,
s.execution_count AS ExecutionCount,
s.max_elapsed_time AS MaxElapsedTime,
ISNULL(s.total_elapsed_time / s.execution_count, 0) AS AvgElapsedTime,
s.creation_time AS LogCreatedOn,
ISNULL(s.execution_count / DATEDIFF(s, s.creation_time, GETDATE()), 0) AS FrequencyPerSec
FROM sys.dm_exec_query_stats s
CROSS APPLY sys.dm_exec_sql_text( s.sql_handle ) t
ORDER BY
s.max_elapsed_time DESC
GO

You can also add WHERE clause to above T-SQL query and filter additionally.

If you have not ran query like this previously on your server I strongly recommend to run this. I bet you will find surprising results.

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

Posted in Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Server DBCC, SQL Stored Procedure, SQL Tips and Tricks, T SQL, Technology ]]> http://blog.sqlauthority.com/2009/01/02/sql-server-2008-2005-find-longest-running-query-tsql/feed/ 24 pinaldave http://blog.sqlauthority.com/2008/11/10/sql-server-check-database-integrity-for-all-databases-of-server/ http://blog.sqlauthority.com/2008/11/10/sql-server-check-database-integrity-for-all-databases-of-server/#comments Mon, 10 Nov 2008 01:30:51 +0000 pinaldave http://sqlauthority.wordpress.com/?p=1489 ]]>

Today we will see quick script which will check integrity of all the database of SQL Server.

EXEC sp_msforeachdb 'DBCC CHECKDB(''?'')'

Above script will return you lots of messages in resultset. If there are any errors in resultset they will be displayed in red text. If everything is black text there is no error. Typical output of above script will be like image included in the article.

Image displayed above is only partial image.

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

Yesterday I received following questions on blog. Ashish Agarwal asked following question.

Hi Pinal,

Can we refresh a database (like we do by right clicking database node in object explorer and clicking on refresh) thru SQL Query?
If yes, can you please tell me the query?

Thanks,
Ashish Agarwal

Answer to above question is NO. It is not possible to do the same task using SQL Query.

However, if you have changed some SP or any other object and if they are cached in the database, database can be refreshed using DBCC commands.

Read my previous article about SQL SERVER – Clear SQL Server Memory Caches.

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

Download SQL Server 2008 Interview Questions and Answers Complete List

Interview is very important event for any person. A good interview leads to good career if candidate is willing to learn. I always enjoy interview questions and answers series. This is my very humble attempt to write SQL Server 2008 interview questions and answers. SQL Server is very large subject and not everything is usually asked in interview. In interview what matters the most is conceptual knowledge and learning attitude.

I have listed all the series in this post so that it can be easily downloaded and used. All the questions are collected and listed in one PDF which is here to download. If you have any question or if you want to add to any of the question please send me mail or write a comment.

SQL SERVER – 2008 – Interview Questions and Answers – Part 1

SQL SERVER – 2008 – Interview Questions and Answers – Part 2

SQL SERVER – 2008 – Interview Questions and Answers – Part 3

SQL SERVER – 2008 – Interview Questions and Answers – Part 4

SQL SERVER – 2008 – Interview Questions and Answers – Part 5

SQL SERVER – 2008 – Interview Questions and Answers – Part 6

SQL SERVER – 2008 – Interview Questions and Answers – Part 7

SQL SERVER – 2008 – Interview Questions and Answers – Part 8

Download SQL Server 2008 Interview Questions and Answers Complete List

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

SQL SERVER – 2008 – Interview Questions and Answers Complete List Download

What is Data Compression?

In SQL SERVE 2008 Data Compression comes in two flavors:

• Row Compression
• Page Compression

Row Compression

Row compression changes the format of physical storage of data. It minimize the metadata (column information, length, offsets etc) associated with each record. Numeric data types and fixed length strings are stored in variable-length storage format, just like Varchar.  (Read More Here)

Page Compression

Page compression allows common data to be shared between rows for a given page. Its uses the following techniques to compress data:

• Row compression.
• Prefix Compression. For every column in a page duplicate prefixes are identified. These prefixes are saved in compression information headers (CI) which resides after page header. A reference number is assigned to these prefixes and that reference number is replaced where ever those prefixes are being used.

Dictionary Compression.

Dictionary compression searches for duplicate values throughout the page and stores them in CI. The main difference between prefix and dictionary compression is that prefix is only restricted to one column while dictionary is applicable to the complete page.

What is use of DBCC Commands?

The Transact-SQL programming language provides DBCC statements that act as Database Console Commands for SQL Server.  DBCC commands are used to perform following tasks.

• Maintenance tasks on database, index, or filegroup.
• Tasks that gather and display various types of information.
• Validation operations on a database, table, index, catalog, filegroup, or allocation of database pages.
• Miscellaneous tasks such as enabling trace flags or removing a DLL from memory.

(Read More Here)

How to find tables without Indexes?

Run following query in Query Editor.

USE <database_name>;
GO
SELECT SCHEMA_NAME(schema_id) AS schema_name
,name AS table_name
FROM sys.tables
WHERE OBJECTPROPERTY(OBJECT_ID,'IsIndexed') = 0
ORDER BY schema_name, table_name;
GO

How to copy the tables, schema and views from one SQL Server to another?

There are multiple ways to do this.

1. “Detach Database” from one server and “Attach Database” to another server.
2. Manually script all the objects using SSMS and run the script on new server.
3. Use Wizard of SSMS. (Read More Here)

How to copy data from one table to another table?

There are multiple ways to do this.

1) INSERT INTO SELECT

This method is used when table is already created in the database earlier and data is to be inserted into this table from another table. If columns listed in insert clause and select clause are same, they are not required to list them.

2) SELECT INTO

This method is used when table is not created earlier and needs to be created when data from one table is to be inserted into newly created table from another table. New table is created with same data types as selected columns.

(Read More Here)

What is Catalog Views?

Catalog views return information that is used by the SQL Server Database Engine. Catalog Views are the most general interface to the catalog metadata and provide the most efficient way to obtain, transform, and present customized forms of this information. All user-available catalog metadata is exposed through catalog views.

What is PIVOT and UNPIVOT?

A Pivot Table can automatically sort, count, and total the data stored in one table or spreadsheet and create a second table displaying the summarized data. The PIVOT operator turns the values of a specified column into column names, effectively rotating a table.

UNPIVOT table is reverse of PIVOT Table. (Read More Here)

What is Filestream?

Filestream allows you to store large objects in the file system and have these files integrated within the database. It enables SQL Server based applications to store unstructured data such as documents, images, audios, videos etc. in the file system. FILESTREAM basically integrates the SQL Server Database Engine with New Technology File System (NTFS); it basically stores the data in varbinary (max) data type. Using this data type, the unstructured data is stored in the NTFS file system and the SQL Server Database Engine manages the link between the Filestream column and the actual file located in the NTFS. Using Transact SQL statements users can insert, update, delete and select the data stored in FILESTREAM enabled tables.

What is Dirty Read ?

A dirty read occurs when two operations say, read and write occurs together giving the incorrect or unedited data. Suppose, A has changed a row, but has not committed the changes. B reads the uncommitted data but his view of the data may be wrong so that is Dirty Read.

What is SQLCMD?

sqlcmd is enhanced version of the isql and osql and it provides way more functionality than other two options. In other words sqlcmd is better replacement of isql (which will be deprecated eventually) and osql (not included in SQL Server 2005 RTM). sqlcmd can work two modes – i) BATCH and ii) interactive modes. (Read More)

What is Aggregate Functions?

Aggregate functions perform a calculation on a set of values and return a single value. Aggregate functions ignore NULL values except COUNT function. HAVING clause is used, along with GROUP BY, for filtering query using aggregate values.

Following functions are aggregate functions.

AVG, MIN, CHECKSUM_AGG, SUM, COUNT, STDEV, COUNT_BIG, STDEVP, GROUPING, VAR, MAX, VARP (Read More Here )

What do you mean by Table Sample?
TABLESAMPLE allows you to extract a sampling of rows from a table in the FROM clause. The rows retrieved are random and they are not in any order. This sampling can be based on a percentage of number of rows. You can use TABLESAMPLE when only a sampling of rows is necessary for the application instead of a full result set. (Read More Here)

What is Row_Number()?
ROW_NUMBER() returns a column as an expression that contains the row’s number within the result set. This is only a number used in the context of the result set, if the result changes, the ROW_NUMBER() will change.

What are Ranking Functions?

Ranking functions return a ranking value for each row in a partition. All the ranking functions are non-deterministic. Different Ranking functions are:

ROW_NUMBER () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition.

RANK () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the rank of each row within the partition of a result set.

DENSE_RANK () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the rank of rows within the partition of a result set, without any gaps in the ranking. (Read More Here )

What is the difference between UNION and UNION ALL?

UNION
The UNION command is used to select related information from two tables, much like the JOIN command. However, when using the UNION command all selected columns need to be of the same data type. With UNION, only distinct values are selected.

UNION ALL
The UNION ALL command is equal to the UNION command, except that UNION ALL selects all values.

The difference between Union and Union all is that Union all will not eliminate duplicate rows, instead it just pulls all rows from all tables fitting your query specifics and combines them into a table. (Read More Here)

What is B-Tree?

The database server uses a B-tree structure to organize index information. B-Tree generally has following types of index pages or nodes:

• root node: A root node contains node pointers to branch nodes which can be only one.
• branch nodes: A branch node contains pointers to leaf nodes or other branch nodes which can be two or more.
• leaf nodes: A leaf node contains index items and horizontal pointers to other leaf nodes which can be many.

© Copyright 2000-2009 Pinal Dave. All Rights Reserved. SQLAuthority.com

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

Imran Mohammed continues to help community of SQL Server with his very enthusiastic writing and deep understanding of SQL Server architecture. Let us read what Imran has to say about how Transaction Log works and Shrinking of Log works.

Question from lauraV

Please help me understand. I am taking a full backup once a day, and transaction logs once every hour. Why is my LDF file not retaining a “normal” size? It continues to grow. I do not want to break the chain and use truncate only, though I have done this and it fixes the problem. I would very much like to understand the underlying problem.
thank you in advance

I suggest to all my readers to read the answer from Imran, this really explains what really goes on behind the scene of Transaction Log. I have highlighted some of the important keylines and keywords in his answer to lauraV.

Answer from Imran Mohammed

@LauraV.

You did not mention which version of SQL Server you are using, Either 2000 or 2005, ( would be easy for us to narrow our answer to questions)

When ever you take transactional log backup, no matter if you scheduled it or if you take it manually, SQL Server by default will empty transactional log. Meaning after the transactional backup ( Be Careful NOT FULL BACKUP) SQL Server will remove inactive transactions from logfile.

Which means your transaction file is empty after you take transactional log backup, Empty doesnot mean your logfile became small, NO. the size of the log file will still be the same but it will be empty, all you have to do is shrink logfile, run below command,

USE database_name
DBCC shrinkfile (logfilename, 1)

and it will shrink the log file to its minimum size possible,

In SQL Server 2000:

Right click database name -> all task -> backup -> in the dialog box, select transactional backup, and click on options ( at the top left side of the box) you will see “remove inactive entries from Transactional log”.

This means when you take transactional Log backup, SQL Server is removing all inactive entries from SQL Server log file. This is default setting.

In SQL Server 2005:

Right Click database name->task ->Backup in the Dialog box, select backup type Transactional backup, and click options tab (at left side up) and under Transaction log section you will see “Truncate the Transaction log”.

Which mean when SQL Server 2005 performs transactional backup it truncates logfile. This is also default setting.

NO matter if you use SQL Server 2000 or SQL Server 2005, SQL Server by default (can be changed) will truncate log after performing Transactional backup.

So simple solution will be shrink log file after you take transactional log backup. You dont have to do it manually You can send this as a response to this transactional bacup job, when ever this job succeed, response to that would be run this script

USE databasename
DBCC shrinkfile ( logfile_name, 1)

That might work.

I will take one more minute to explain what is this active and inactive transaction in the logfile . Please correct me if I am wrong.

This is how SQL Server works,

Note from Pinal – Following 4 paragraph is the most interesting part of whole discussion.

When a transaction comes to SQL Server, it first comes to transactional log buffer, and then it is hardened to disk ( log file, .ldf ) and then it is written to data file ( .mdf). Then we say the transaction is committed or it is inactive, because the transaction performed all the actions that it should.

On the other hand, when a transaction comes to SQL Server and it is entered into log buffer and also in transactional log, but not yet entered in data file, its still in the process, then we will say this transaction as active transaction.

One important point to think is, all the inactive transactions in the log file ( transactions which completed their tasks and are entered in data file) are also present in data file, and SQL Server is smart enough to think, inactive transactions are already in data file and also, they have been backed up( by transactional log backup) hence it thinks, this is the time to get rid of this data and it removes all the inactive transactions.

But for Active transactions, which are either incomplete or could not complete because of disaster ( sudden power failure….) will be stored in transactional log and will be called acive transactions untill they are entered in data file.

This will be little bit confusing…

Read more about this in books online.

Hope this helps.
Imran.

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

If you are DBA who are involved with Database Maintenance and file group maintenance, you must have experience that many times DBCC SHRINKFILE operations takes long time but any other operations with Database are relative quicker. Rebuilding index is quite resource intensive task but that happens faster than DBCC SHRINKFILE.

Well, answer to this is very simple. DBCC SHRINKFILE is a single threaded operation. A single threaded operation does not take advantage of multiple CPUs and have no effect how many RAM are available. Hyperthreaded CPU even provides worst performance.

If you rebuild indexes before you run DBCC SHRINKFILE operations, shrinking file operations will take relatively less time. Rebuilding Index operations takes advantage of multiple CPUs.

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

If SQL Server is running slow and operations are throwing errors due to lack of memory, it is necessary to look into memory issue. If SQL Server is restarted all the cache memory is automatically cleaned up. In production server it is not possible to restart the server. In this scenario following three commands can be very useful.

When executed following three commands will free up memory for SQL Server by cleaning up its cache.

DBCC FREESYSTEMCACHE
DBCC FREESESSIONCACHE
DBCC FREEPROCCACHE

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

Many times we need to know what is the current identity of the column. I have found one of my developer using aggregated function MAX() to find the current identity.

USE AdventureWorks
GO
SELECT MAX(AddressID)
FROM Person.Address
GO

However, I prefer following DBCC command to figure out current identity.

USE AdventureWorks
GO
DBCC CHECKIDENT ('Person.Address')
GO

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

Just a day ago, I received email from regular reader Rajiv Kayasthy about a script which demonstrates the A Simple Way To Defragment All Indexes In A Database That Is Fragmented Above A Declared Threshold. He found this script on TechNet BOL and was attempting to run on SQL Server but was getting continuous error

Msg 2501, Level 16, State 45, Line 1
Cannot find a table or object with the name “TableName”. Check the system catalog.

After looking at the script provided on BOL I found that it has very small error. It was retrieving data without prefixing database schema. I have modified original script and corrected it to run on SQL Server 2005.

Following corrected script demonstrates Simple Way To Defragment All Indexes In A Database That Is Fragmented Above A Declared Threshold.

/* Originally created by Microsoft */
/* Error corrected by Pinal Dave (http://www.SQLAuthority.com) */
-- Specify your Database Name
USE AdventureWorks;
GO
-- Declare variables
SET NOCOUNT ON;
DECLARE @tablename VARCHAR(128);
DECLARE @execstr VARCHAR(255);
DECLARE @objectid INT;
DECLARE @indexid INT;
DECLARE @frag decimal;
DECLARE @maxfrag decimal;
-- Decide on the maximum fragmentation to allow for.
SELECT @maxfrag = 30.0;
-- Declare a cursor.
DECLARE tables CURSOR FOR
SELECT CAST(TABLE_SCHEMA AS VARCHAR(100))
+'.'+CAST(TABLE_NAME AS VARCHAR(100))
AS Table_Name
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE';
-- Create the table.
CREATE TABLE #fraglist (
ObjectName CHAR(255),
ObjectId INT,
IndexName CHAR(255),
IndexId INT,
Lvl INT,
CountPages INT,
CountRows INT,
MinRecSize INT,
MaxRecSize INT,
AvgRecSize INT,
ForRecCount INT,
Extents INT,
ExtentSwitches INT,
AvgFreeBytes INT,
AvgPageDensity INT,
ScanDensity decimal,
BestCount INT,
ActualCount INT,
LogicalFrag decimal,
ExtentFrag decimal);
-- Open the cursor.
OPEN tables;
-- Loop through all the tables in the database.
FETCH NEXT
FROM tables
INTO @tablename;
WHILE @@FETCH_STATUS = 0
BEGIN;
-- Do the showcontig of all indexes of the table
INSERT INTO #fraglist
EXEC ('DBCC SHOWCONTIG (''' + @tablename + ''')
WITH FAST, TABLERESULTS, ALL_INDEXES, NO_INFOMSGS');
FETCH NEXT
FROM tables
INTO @tablename;
END;
-- Close and deallocate the cursor.
CLOSE tables;
DEALLOCATE tables;
-- Declare the cursor for the list of indexes to be defragged.
DECLARE indexes CURSOR FOR
SELECT ObjectName, ObjectId, IndexId, LogicalFrag
FROM #fraglist
WHERE LogicalFrag >= @maxfrag
AND INDEXPROPERTY (ObjectId, IndexName, 'IndexDepth') > 0;
-- Open the cursor.
OPEN indexes;
-- Loop through the indexes.
FETCH NEXT
FROM indexes
INTO @tablename, @objectid, @indexid, @frag;
WHILE @@FETCH_STATUS = 0
BEGIN;
PRINT 'Executing DBCC INDEXDEFRAG (0, ' + RTRIM(@tablename) + ',
' + RTRIM(@indexid) + ') - fragmentation currently '
+ RTRIM(CONVERT(VARCHAR(15),@frag)) + '%';
SELECT @execstr = 'DBCC INDEXDEFRAG (0, ' + RTRIM(@objectid) + ',
' + RTRIM(@indexid) + ')';
EXEC (@execstr);
FETCH NEXT
FROM indexes
INTO @tablename, @objectid, @indexid, @frag;
END;
-- Close and deallocate the cursor.
CLOSE indexes;
DEALLOCATE indexes;
-- Delete the temporary table.
DROP TABLE #fraglist;
GO

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

There are ROWCOUNT rows in PAGECOUNT pages for object ‘OBJECT’.

This message is displayed when DBCC command is ran for any database. It is harmless and displayed for information purpose only. For each database DBCC commands displays number of rows and number of pages it is using. DBCC CHECKALLOC is exception for this messages.

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

All DBA and Developers must have observed when any variable length column is dropped from table, it does not reduce the size of table. Table size stays the same till Indexes are reorganized or rebuild. There is also DBCC command DBCC CLEANTABLE, which can be used to reclaim any space previously occupied with variable length columns. Variable length columns include varchar, nvarchar, varchar(max), nvarchar(max), varbinary, varbinary(max), text, ntext, image, sql_variant, and xml. Space can be reclaimed when variable length column is also modified to lesser length.

DBCC command for reclaiming space is very simple. Following example is for AdventureWorks database and Person.Contact table.

DBCC CLEANTABLE ('AdventureWorks','Person.Contact', 0)

The result of DBCC is displayed below.
DBCC execution completed. If DBCC printed error messages, contact your system administrator.
DBCC is fully logged operation. It also does not affect temp tables and system tables.

Reference : Pinal Dave (http://blog.SQLAuthority.com), BOL – DBCC CLEANTABLE

One of my friend involved with large business of medical transcript invited me for SQL Server improvement talk last weekend. I had great time talking with group of DBA and developers. One of the topic which was discussed was how to find out Fragmentation Information for any table in one particular database. For SQL Server 2000 it was easy to find using DBCC SHOWCONTIG command. DBCC SHOWCONTIG has some limitation for SQL Server 2000.

SQL Server 2005 has sys.dm_db_index_physical_stats dynamic view which returns size and fragmentation information for the data and indexes of the specified table or view. You can run following T-SQL for any database to know detailed information of the database.
SELECT *
FROM sys.dm_db_index_physical_stats(DB_ID(), OBJECT_ID('test_contig'), NULL, NULL , 'DETAILED')

Above query returns lots of information, most of the time we only need to know Tablename, IndexName and Percentage of Fragmentation. Following query returns only three most important details mentioned earlier. I have added an extra condition where results are filtered where average fragmentation is greater than 20%.

SELECT OBJECT_NAME(i.OBJECT_ID) AS TableName,
i.name AS IndexName,
indexstats.avg_fragmentation_in_percent
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'DETAILED') indexstats
INNER JOIN sys.indexes i ON i.OBJECT_ID = indexstats.OBJECT_ID
AND i.index_id = indexstats.index_id
WHERE indexstats.avg_fragmentation_in_percent > 20

The results will help DBA to make necessary reports.

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

DBCC CHECKDB checks the logical and physical integrity of all the objects in the specified database. If DBCC CHECKDB ran on database user should not run DBCC CHECKALLOC, DBCC CHECKTABLE, and DBCC CHECKCATALOG on database as DBCC CHECKDB includes all the three command. Usage of these included DBCC commands is listed below.

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

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

DBCC CHECKCATALOG – Checks for catalog consistency within the specified database. The database must be online.

Along with above three DBCC commands it also runs following two tasks to check the validity database (physical as well logical) i.e. validates the contents of every indexed view in the database and Validates the Service Broker data in the database.

If database DBCC check has returned any errors, the best solution is to RESTORE DATABASE from BACKUP. (Additional reading : SQL Backup and Restore). There is additional keyword REPAIR with DBCC CHECKDB which can be used to repair database but it is not recommended. I will write additional articles on this subject.

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

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SQL SERVER – 2005 – Search Stored Procedure Code – Search Stored Procedure Text

SQL SERVER – 2005 – Find Tables With Foreign Key Constraint in Database

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SQL SERVER – 2005 – Start Stop Restart SQL Server From Command Prompt

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