Microsoft's SQL Server is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. It originated from the Sybase SQL Server codebase, which is why both products use the extension of SQL called Transact-SQL (T-SQL).

learn more… | top users | synonyms (2)

34
votes
4answers
14k views

Why would SET ARITHABORT ON dramatically speed up a query?

The query is a single select containing a lot of grouping levels and aggragate operations. With SET ARITHABORT ON is takes less than a second, otherwise it takes several minutes. We have seen this ...
21
votes
4answers
1k views

Does the order of columns in a table's definition matter?

When defining a table, it's helpful to order the columns in logical groups and the groups themselves by purpose. The logical ordering of columns in a table conveys meaning to the developer and is an ...
15
votes
5answers
2k views

Why use an int as a lookup table's primary key?

I want to know why I should use an int as a lookup table's primary key instead of just using the lookup value as the primary key (which in most cases would be a string). I understand that using a ...
10
votes
2answers
7k views

What is a Clustered Index?

I need a short explaining of clustered index. What is a clustered index? What are best practices for using the clustered index?
6
votes
2answers
2k views

Which one is more efficient: select from linked server or insert into linked server?

Suppose I have to export data from one server to another (through linked servers). Which statement will be more efficient? Executing in source server: INSERT INTO ...
13
votes
3answers
1k views

Is there any benefit to defragmenting SQL indexes in a SAN environment?

Our SQL server lives on a SAN. It contains dozens of OLTP databases, some with several tables containing over 1m records. We have been running Ola Hallengren's index maintenance scripts weekly, and ...
3
votes
1answer
154 views

VLDB with large quantity of data file imports

I am a little out of my league with this scenario and hope this community can help get me on the right direction. I have recently been tasked with re-designing and implementing a database application ...
2
votes
5answers
5k views

Cannot start SqlLocalDB instance with my Windows account

I'm the administrator and simply run the command: sqllocaldb start v11.0 Result: Start of LocalDB instance "v11.0" failed because of the following error: Error occurred during LocalDB instance ...
12
votes
3answers
3k views

Find out what queries are causing the biggest amount of network traffic

On a production SQL server I am seeing intermittent enormous spikes in data traffic. Up to 200Mbit/s which is causing NETWORK IO waits which in turn cause query timeouts. How can I find out what ...
9
votes
3answers
6k views

What can cause a mirroring session to timeout then failover? SQL Server 2005

We have two production SQL Servers running SQL Server 2005 SP4 with cumulative update 3. Both servers run on physical machines that are identical. DELL PowerEdge R815 with 4 x 12 core CPUs and 512GB ...
7
votes
2answers
3k views

Why index REBUILD does not reduce index fragmentatation?

I have used ALTER INDEX REBUILD to remove index fragmentation. In some cases REBUILD does not seem to remove this fragmentation. What are the reasons why REBUILD does not remove fragmentation? It ...
6
votes
3answers
5k views

What's the easiest way to create a temp table in SQL Server that can hold the result of a stored procedure?

Many times I need to write something like the following when dealing with SQL Server. create table #table_name ( column1 int, column2 varchar(200) ... ) insert into #table_name execute ...
4
votes
1answer
2k views

SIMPLE or FULL recovery model for databases?

When should I use the full recovery model and when should I use the simple recovery model for databases? I always used the full recovery model because it is the default, but today i encountered this ...
9
votes
1answer
2k views

SQL query for combinations without repetition

I need a query which can be used in (or as) a function and retrieves all combinations of n values. And I need all combinations of length k where k = 1..n. Extended sample input and result so input ...
8
votes
2answers
3k views

What is blocking and how does it happen?

I tried to find some information about blocking in SQL Server, but I could not find a concise explanation for what it is and how it happens. Could you please enlighten me?
7
votes
5answers
23k views

Restore SQL Server 2012 backup to a SQL Server 2008 database?

Is there a way to restore a SQL Server 2012 database backup to a SQL Server 2008? I tried to attach file, it does not work.
6
votes
2answers
1k views

'Conversion failed' error with ORDER BY CASE expression

I have the following Stored Procedure that works great EXCEPT when I set the 'OrderBy' to 'OrderNumber'. I get the following error: Conversion failed when converting the nvarchar value 'SK11270' to ...
5
votes
1answer
2k views

SQL Server: hierarchy of permissions for schema?

We have several databases under development and I would like to start using SQL Server schemas for permission management and logical grouping of database objects. Under Schema Properties there is ...
3
votes
3answers
2k views

How to move data from big table

There is a big table (5-6 million records). I have to move 90% of old records to other database(table). Solution?
10
votes
1answer
817 views

DELETE vs TRUNCATE

I am trying to get a greater understanding on the differences between the DELETE and TRUNCATE commands. My understanding of the internals goes something along the lines of: DELETE -> the database ...
10
votes
2answers
3k views

How to know when/if I have too many indexes?

Running Microsoft SQL Server Profiler every now and then, it suggests me with a bunch of new indexes and statistics to create ("...97% estimated improvement..."). From my understanding every added ...
8
votes
1answer
160 views

Are the cost percentages in this SQL Server plan over 100% for a valid reason?

I'm looking through the plan cache, looking for low-hanging optimization fruit and came across this snippet: Why are many of the costs listed above 100% ? Shouldn't that be impossible?
7
votes
3answers
282 views

Would it be considered as a bad practice to have multiple nullable FKs on a table in SQL Server

On my database structure in SQL Server, I have 3 types of products which requires different information about the order. So, I created one Customers table and three different orders tables: ...
6
votes
2answers
2k views

Is it possible to backup and restore part of a database in sql-server?

We have a sql-server 2005 database that we regularly transfer from our client site to ours. This takes a long time because we don't have a direct connection and have to transfer the file over their ...
5
votes
4answers
2k views

SQL Server script to delete accounts no longer in Active Directory

We have a SQL Server 2000 that will shortly be migrated to SQL Server 2005. It has years of Windows Authentication accounts created that no longer exist in Active Directory, which prevent the Copy ...
5
votes
1answer
1k views

Kerberos authentication not working with Linked Servers in SQL Server 2012

I am setting up a DEV/TEST environment using 2 SQL Servers running SQL Server 2012 on Windows Server 2012. We are moving from SQL Server 2005 on Windows Server 2008, where we already have this ...
3
votes
1answer
659 views

Running queries with SQLCMD vs. Running queries with SSMS

I've noticed something which i'm not sure about. can it be that running queries directly with SSMS is much faster than running queries with SQLCMD? I've noticed that the results of queries that ran ...
3
votes
2answers
503 views

Restore a Database into a Current Database and merge

I want to know how, or if it is possible, to backup a database then should the user wish, restore that database at a later date and merge it with the one they are currently using. Both Databases will ...
3
votes
1answer
273 views

Shrinking log file

Some of the sql log files (idf) are hugh like 5gb. Found a article (http://extended64.com/blogs/rhoffman/archive/2009/06/11/shrink-sql-server-2008-database-log-file-script.aspx) but not sure why he ...
3
votes
3answers
2k views

NULLs in a composite primary key - SQL Server

I'm trying to work out the best way of creating SQL Server primary keys, foreign keys and constraints to accurately represent my data model in LINQ / Entity Data Objects. Let's assume - for the ...
3
votes
1answer
1k views

Is SQL Server Backup single or multi-threaded?

If you perform a... BACKUP DATABASE [DB_Name] TO DISK=N'c:\backups\db_name.bak' WITH STATS=10 Will that perform a single or multi-threaded write? Our Server support company advised us that if we ...
2
votes
3answers
16k views

SQL Server 2008 R2 High memory usage

I have SQL Server 2008 R2 that runs multiple jobs over night, the problem is SQL Server will eat up all RAM and CPU, then it will not release the RAM resources after the job finishes, as a workaround ...
1
vote
1answer
148 views

Restoring a differential backup in SQL server 2005

I have created a full back up of my database by executing the line below in my application: Dim Query As String = "backup database Ari to disk='G:\Documents and Settings\i\Desktop\BKAR\" & ...
0
votes
1answer
1k views

How to copy backup files to remote share in SQL Server Agent job without AD/domain accounts involvement?

MS SQL Server 2012... with nightly databases backups to the same/local as SQL Server machine... I am trying to add another SQL Server Agent Job to copy the .bak files to remote (non-windows, i.e. ...
-4
votes
1answer
425 views

Why does a VIEW with a CLUSTERED index not use the index?

I have a view that has a clustered index along with other non-clustered indexes. A simple SELECT query does not use any of the indexes even when I select an indexed column. What could be the ...
188
votes
4answers
32k views

What's the difference between a temp table and table variable in SQL Server?

This seems to be an area with quite a few myths and conflicting views. So what is the difference between a table variable and a local temporary table in SQL Server?
41
votes
5answers
10k views

When to use TINYINT over INT?

In general, I always use Ints. I know that in theory this is not the best practice, though, since you should use the smallest data type that will be guaranteed to store the data. For example, it's ...
38
votes
8answers
10k views

What's the difference between a CTE and a Temp Table?

What is the difference between a Common Table Expression (CTE) and a temp table? And when should I use one over the other? CTE WITH cte (Column1, Column2, Column3) AS ( SELECT Column1, Column2, ...
25
votes
2answers
50k views

How to the get current date without the time part

In SQL Server 2005 how do I get the current date without the time part? I have been using GETDATE() but would like it to have a time of 00:00:00.0
31
votes
11answers
3k views

How can I track database dependencies?

As internal applications evolve over a number of years, you occasionally find there are a number of tables that people believe are no longer relevant and want to cull. What are the practical methods ...
12
votes
2answers
4k views

What are the best practices for running SQL Server in a Virtual Machine?

What are the best practices for running SQL Server in a Virtual Machine? My on-line transaction activities are very low, but there is a high amount of data processing for the purpose of providing ...
20
votes
3answers
14k views

What risks are there if we enable read committed snapshot in sql-server?

I have read here that some extra data will be stored per row so we might see a performance degradation but what other risks are there? eg. Will this affect recovery of the database? Is there anything ...
16
votes
1answer
3k views

Connection pools being reset with Error: 18056, Severity: 20, State: 46. & Perfmon Counters not showing

We are using SQL authentication & .net 4.0 Connection strings to connect to an Enterprise Edition 2012 SP1 SQL Server on a windows 2008r2 Enterprise Server. We use about 50 Servers split into 8 ...
16
votes
3answers
4k views

Running total with count?

As the title suggests I need some help getting a running total in T-SQL. The problem is that the sum I need to do is the sum of a count: sum(count (distinct (customers))) Say if I ran the count ...
14
votes
2answers
1k views

Why does DELETE leave a lingering effect on performance?

At the end is a test script for comparing the performance between a @table variable and a #temp table. I think I've set it up correctly - the performance timings are taken outside of the ...
11
votes
2answers
2k views

Handling growing number of Tenants in Multi-tenant Database Architecture

Handling a modest number of customers (tenants) in a common server with separate databases for each tenant's instance of the application is relatively straightforward and is normally the correct way ...
10
votes
6answers
5k views

Optimal drive configuration for SQL Server 2008R2

I have a fairly busy database server running SQL Server 2008 R2 that has the following setup: SATA RAID 1 (2 Drives) - OS / Programs SAS RAID 10 (4 Drives) - Sql Database Files (data and logs) SAS ...
28
votes
5answers
8k views

When should I use a unique constraint instead of a unique index?

When I want a column to have distinct values, I can either use a constraint create table t1( id int primary key, code varchar(10) unique NULL ); go or I can use a unique index create table t2( id ...
18
votes
1answer
3k views

Why is using a table variable more than twice as fast as a #temp table in this specific case?

I was looking at the article here Temporary Tables vs. Table Variables and Their Effect on SQL Server Performance and on SQL Server 2008 was able to reproduce similar results to those shown there for ...
14
votes
2answers
13k views

How to find the SQL statements which caused the tempdb grew huge?

The tempdb of an server (SQL Server 2008) increases to 500+G several times every month. Is it possilbe to find out which SQL statements cause the problems? (The problem is usually not caused by create ...