Hidden Features of SQL Server

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What are some hidden features of SQL Server?

For example, undocumented system stored procedures, tricks to do things which are very useful but not documented enough?

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Answers

Thanks to everybody for all the great answers!

Stored Procedures

• sp_msforeachtable: Runs a command with '?' replaced with each table name (v6.5 and up)
• sp_msforeachdb: Runs a command with '?' replaced with each database name (v7 and up)
• sp_who2: just like sp_who, but with a lot more info for troubleshooting blocks (v7 and up)
• sp_helptext: If you want the code of a stored procedure, view & UDF
• sp_tables: return a list of all tables and views of database in scope.
• sp_stored_procedures: return a list of all stored procedures
• xp_sscanf: Reads data from the string into the argument locations specified by each format argument.
• xp_fixeddrives:: Find the fixed drive with largest free space
• sp_help: If you want to know the table structure, indexes and constraints of a table. Also views and UDFs. Shortcut is Alt+F1

Snippets

• Returning rows in random order
• All database User Objects by Last Modified Date
• Return Date Only
• Find records which date falls somewhere inside the current week.
• Find records which date occurred last week.
• Returns the date for the beginning of the current week.
• Returns the date for the beginning of last week.
• See the text of a procedure that has been deployed to a server
• Drop all connections to the database
• Table Checksum
• Row Checksum
• Drop all the procedures in a database
• Re-map the login Ids correctly after restore
• Call Stored Procedures from an INSERT statement
• Find Procedures By Keyword
• Drop all the procedures in a database
• Query the transaction log for a database programmatically.

Functions

• HashBytes()
• EncryptByKey
• PIVOT command

Misc

• Connection String extras
• TableDiff.exe
• Triggers for Logon Events (New in Service Pack 2)
• Boosting performance with persisted-computed-columns (pcc).
• DEFAULT_SCHEMA setting in sys.database_principles
• Forced Parameterization
• Vardecimal Storage Format
• Figuring out the most popular queries in seconds
• Scalable Shared Databases
• Table/Stored Procedure Filter feature in SQL Management Studio
• Trace flags
• Number after a GO repeats the batch
• Security using schemas
• Encryption using built in encryption functions, views and base tables with triggers

Answer 1

In Management Studio, you can put a number after a GO end-of-batch marker to cause the batch to be repeated that number of times:

PRINT 'X'
GO 10

Will print 'X' 10 times. This can save you from tedious copy/pasting when doing repetitive stuff.

Answer 2

A lot of SQL Server developers still don't seem to know about the OUTPUT clause (SQL Server 2005 and newer) on the DELETE, INSERT and UPDATE statement.

It can be extremely useful to know which rows have been INSERTed, UPDATEd, or DELETEd, and the OUTPUT clause allows to do this very easily - it allows access to the "virtual" tables called inserted and deleted (like in triggers):

DELETE FROM (table)
OUTPUT deleted.ID, deleted.Description
WHERE (condition)

If you're inserting values into a table which has an INT IDENTITY primary key field, with the OUTPUT clause, you can get the inserted new ID right away:

INSERT INTO MyTable(Field1, Field2)
OUTPUT inserted.ID
VALUES (Value1, Value2)

And if you're updating, it can be extremely useful to know what changed - in this case, inserted represents the new values (after the UPDATE), while deleted refers to the old values before the UPDATE:

UPDATE (table)
SET field1 = value1, field2 = value2
OUTPUT inserted.ID, deleted.field1, inserted.field1
WHERE (condition)

If a lot of info will be returned, the output of OUTPUT can also be redirected to a temporary table or a table variable (OUTPUT INTO @myInfoTable).

Extremely useful - and very little known!

Marc

Answer 3

sp_msforeachtable: Runs a command with '?' replaced with each table name. e.g.

exec sp_msforeachtable "dbcc dbreindex('?')"

You can issue up to 3 commands for each table

exec sp_msforeachtable
    @Command1 = 'print ''reindexing table ?''',
    @Command2 = 'dbcc dbreindex(''?'')',
    @Command3 = 'select count (*) [?] from ?'

Also, sp_MSforeachdb

Answer 4

Connection String extras:

MultipleActiveResultSets=true;

This makes ADO.Net 2.0 and above read multiple, forward-only, read-only results sets on a single database connection, which can improve performance if you're doing a lot of reading. You can turn it on even if you're doing a mix of query types.

Application Name=MyProgramName

Now when you want to see a list of active connections by querying the sysprocesses table, your program's name will appear in the program_name column instead of ".Net SqlClient Data Provider"

Answer 5

TableDiff.exe

• Table Difference tool allows you to discover and reconcile differences between a source and destination table or a view. Tablediff Utility can report differences on schema and data. The most popular feature of tablediff is the fact that it can generate a script that you can run on the destination that will reconcile differences between the tables.

Link

Answer 6

A less known TSQL technique for returning rows in random order:

-- Return rows in a random order
SELECT 
    SomeColumn 
FROM 
    SomeTable
ORDER BY 
    CHECKSUM(NEWID())

Answer 7

In Management Studio, you can quickly get a comma-delimited list of columns for a table by :

1. In the Object Explorer, expand the nodes under a given table (so you will see folders for Columns, Keys, Constraints, Triggers etc.)
2. Point to the Columns folder and drag into a query.

This is handy when you don't want to use heinous format returned by right-clicking on the table and choosing Script Table As..., then Insert To... This trick does work with the other folders in that it will give you a comma-delimited list of names contained within the folder.

Answer 8

Row Constructors

You can insert multiple rows of data with a single insert statement.

INSERT INTO Colors (id, Color)
VALUES (1, 'Red'),
       (2, 'Blue'),
       (3, 'Green'),
       (4, 'Yellow')

Answer 9

If you want to know the table structure, indexes and constraints:

sp_help 'TableName'

Answer 10

HashBytes() to return the MD2, MD4, MD5, SHA, or SHA1 hash of its input.

Answer 11

Figuring out the most popular queries

• With sys.dm_exec_query_stats, you can figure out many combinations of query analyses by a single query.

Link with the commnad

select * from sys.dm_exec_query_stats 
order by execution_count desc

Answer 12

The spatial results tab can be used to create art.

enter link description here http://michaeljswart.com/wp-content/uploads/2010/02/venus.png

Answer 13

EXCEPT and INTERSECT

Instead of writing elaborate joins and subqueries, these two keywords are a much more elegant shorthand and readable way of expressing your query's intent when comparing two query results. New as of SQL Server 2005, they strongly complement UNION which has already existed in the TSQL language for years.

The concepts of EXCEPT, INTERSECT, and UNION are fundamental in set theory which serves as the basis and foundation of relational modeling used by all modern RDBMS. Now, Venn diagram type results can be more intuitively and quite easily generated using TSQL.

Answer 14

I know it's not exactly hidden, but not too many people know about the PIVOT command. I was able to change a stored procedure that used cursors and took 2 minutes to run into a speedy 6 second piece of code that was one tenth the number of lines!

Answer 15

useful when restoring a database for Testing purposes or whatever. Re-maps the login ID's correctly:

EXEC sp_change_users_login 'Auto_Fix', 'Mary', NULL, 'B3r12-36'

Answer 16

Drop all connections to the database:

Use Master
Go

Declare @dbname sysname

Set @dbname = 'name of database you want to drop connections from'

Declare @spid int
Select @spid = min(spid) from master.dbo.sysprocesses
where dbid = db_id(@dbname)
While @spid Is Not Null
Begin
        Execute ('Kill ' + @spid)
        Select @spid = min(spid) from master.dbo.sysprocesses
        where dbid = db_id(@dbname) and spid > @spid
End

Answer 17

Table Checksum

Select CheckSum_Agg(Binary_CheckSum(*)) From Table With (NOLOCK)

Row Checksum

Select CheckSum_Agg(Binary_CheckSum(*)) From Table With (NOLOCK) Where Column = Value

Answer 18

I'm not sure if this is a hidden feature or not, but I stumbled upon this, and have found it to be useful on many occassions. You can concatonate a set of a field in a single select statement, rather than using a cursor and looping through the select statement.

Example:

DECLARE @nvcConcatonated nvarchar(max)
SET @nvcConcatonated = ''

SELECT @nvcConcatonated = @nvcConcatonated + C.CompanyName + ', '
FROM tblCompany C
WHERE C.CompanyID IN (1,2,3)

SELECT @nvcConcatonated

Results:

Acme, Microsoft, Apple,

Answer 19

If you want the code of a stored procedure you can:

sp_helptext 'ProcedureName'

(not sure if it is hidden feature, but I use it all the time)

Answer 20

A stored procedure trick is that you can call them from an INSERT statement. I found this very useful when I was working on an SQL Server database.

CREATE TABLE #toto (v1 int, v2 int, v3 char(4), status char(6))
INSERT #toto (v1, v2, v3, status) EXEC dbo.sp_fulubulu(sp_param1)
SELECT * FROM #toto
DROP TABLE #toto

Answer 21

In SQL Server 2005/2008 to show row numbers in a SELECT query result:

SELECT ( ROW_NUMBER() OVER (ORDER BY OrderId) ) AS RowNumber,
        GrandTotal, CustomerId, PurchaseDate
FROM Orders

ORDER BY is a compulsory clause. The OVER() clause tells the SQL Engine to sort data on the specified column (in this case OrderId) and assign numbers as per the sort results.

Answer 22

Useful for parsing stored procedure arguments: xp_sscanf

Reads data from the string into the argument locations specified by each format argument.

The following example uses xp_sscanf to extract two values from a source string based on their positions in the format of the source string.

DECLARE @filename varchar (20), @message varchar (20)
EXEC xp_sscanf 'sync -b -fproducts10.tmp -rrandom', 'sync -b -f%s -r%s', 
  @filename OUTPUT, @message OUTPUT
SELECT @filename, @message

Here is the result set.

-------------------- -------------------- 
products10.tmp        random

Answer 23

Return Date Only

Select Cast(Floor(Cast(Getdate() As Float))As Datetime)

or

Select DateAdd(Day, 0, DateDiff(Day, 0, Getdate()))

Answer 24

dm_db_index_usage_stats

This allows you to know if data in a table has been updated recently even if you don't have a DateUpdated column on the table.

SELECT OBJECT_NAME(OBJECT_ID) AS DatabaseName, last_user_update,*
FROM sys.dm_db_index_usage_stats
WHERE database_id = DB_ID( 'MyDatabase')
AND OBJECT_ID=OBJECT_ID('MyTable')

Code from: http://blog.sqlauthority.com/2009/05/09/sql-server-find-last-date-time-updated-for-any-table/

Information referenced from: SQL Server - What is the date/time of the last inserted row of a table?

Available in SQL 2005 and later

Answer 25

Here are some features I find useful but a lot of people don't seem to know about:

sp_tables

Returns a list of objects that can be queried in the current environment. This means any object that can appear in a FROM clause, except synonym objects.

Link

sp_stored_procedures

Returns a list of stored procedures in the current environment.

Link

Answer 26

Find records which date falls somewhere inside the current week.

where dateadd( week, datediff( week, 0, TransDate ), 0 ) =
dateadd( week, datediff( week, 0, getdate() ), 0 )

Find records which date occurred last week.

where dateadd( week, datediff( week, 0, TransDate ), 0 ) =
dateadd( week, datediff( week, 0, getdate() ) - 1, 0 )

Returns the date for the beginning of the current week.

select dateadd( week, datediff( week, 0, getdate() ), 0 )

Returns the date for the beginning of last week.

select dateadd( week, datediff( week, 0, getdate() ) - 1, 0 )

Answer 27

Not so much a hidden feature but setting up key mappings in Management Studio under Tools\Options\Keyboard: Alt+F1 is defaulted to sp_help "selected text" but I cannot live without the adding Ctrl+F1 for sp_helptext "selected text"

Answer 28

Persisted-computed-columns

• Computed columns can help you shift the runtime computation cost to data modification phase. The computed column is stored with the rest of the row and is transparently utilized when the expression on the computed columns and the query matches. You can also build indexes on the PCC’s to speed up filtrations and range scans on the expression.

Link

Answer 29

There are times when there's no suitable column to sort by, or you just want the default sort order on a table and you want to enumerate each row. In order to do that you can put "(select 1)" in the "order by" clause and you'd get what you want. Neat, eh?

select row_number() over (order by (select 1)), * from dbo.Table as t

Answer 30

Simple encryption with EncryptByKey