I am using SQL Server 2012. I guess what I am asking is should I continue on the path of researching the ability to create a SP (or UDF, but with #Temp tables probably involved, I was thinking SP) in order to have a reusable object to determine the median?
I hope this isn't too generic of a question, and is hosed, but I have spent some time researching the ability to determine a median value. Some possible hurdles include the need to pass in a string representation of the query that will return the data that I wish to perform the median on.
Anyone attempt this in the past?
Here is a stored proc I use to generate some quick stats.
Simply pass a Source, Measure and/or Filter.
CREATE PROCEDURE [dbo].[prc-Dynamic-Stats](#Table varchar(150),#Fld varchar(50), #Filter varchar(500))
-- Syntax: Exec [dbo].[prc-Dynamic-Stats] '[Chinrus-Series].[dbo].[DS_Treasury_Rates]','TR_Y10','Year(TR_Date)>2001'
As
Begin
Set NoCount On;
Declare #SQL varchar(max) =
'
;with cteBase as (
Select RowNr=Row_Number() over (Order By ['+#Fld+'])
,Measure = ['+#Fld+']
From '+#Table+'
Where '+case when #Filter='' then '1=1' else #Filter end+'
)
Select RecordCount = Count(*)
,DistinctCount = Count(Distinct A.Measure)
,SumTotal = Sum(A.Measure)
,Minimum = Min(A.Measure)
,Maximum = Max(A.Measure)
,Mean = Avg(A.Measure)
,Median = Max(B.Measure)
,Mode = Max(C.Measure)
,StdDev = STDEV(A.Measure)
From cteBase A
Join (Select Measure From cteBase where RowNr=(Select Cnt=count(*) from cteBase)/2) B on 1=1
Join (Select Top 1 Measure,Hits=count(*) From cteBase Group By Measure Order by 2 desc ) C on 1=1
'
Exec(#SQL)
End
Returns
RecordCount DistinctCount SumTotal Minimum Maximum Mean Median Mode StdDev
3615 391 12311.81 0.00 5.44 3.4057 3.57 4.38 1.06400795277565
You may want to take a look at a response that I had to this post. In short, if you're comfortable with C# or VB .NET, you could create a user defined CLR aggregate. We use CLR implementations for quite a few things, especially statistical methods that you may see in other platforms like SAS, R, etc.
This is easily accomplished by creating a User-Defined Aggregate (UDA) via SQLCLR. If you want to see how to do it, or even just download the UDA, check out the article I wrote about it on SQL Server Central: Getting The Most Out of SQL Server 2005 UDTs and UDAs (please note that the site requires free registration in order to read their content).
Or, it is also available in the Free version of the SQL# SQLCLR library (which I created, but again, it is free) available at http://SQLsharp.com/. It is called Agg_Median.
If using SQL Server 2008 or newer (which you are), you can write a function that accepts a table-valued parameter as input.
Create Type MedianData As Table ( DataPoint Int )
Create Function CalculateMedian ( #MedianData MedianData ReadOnly )
Returns Int
As
Begin
-- do something with #MedianData which is a table
End
How can I use the result of a select statement into another statement in a stored procedure in SQL Server? I am try to write this code
CREATE procedure [dbo].[ShowRequest] (#Id int)
AS
SELECT
Request.RequestId,
Request.UserId
INTO
reqTable
FROM
[User],[Request]
WHERE
Request.UserId = [User].UserId
AND
Request.RequestId = Id
/*another selection*/
SELECT
RequestProduct.ProductName
FROM
RequestProduct
/*ERROR:The multi-part identifier "ReqTable.id" could not be bound*/
WHERE
RequestProduct.RequestId = ReqTable.[id]
Try this:
CREATE procedure [dbo].[ShowRequest] (#Id int)
AS
SELECT
Request.RequestId,
Request.UserId
INTO
reqTable
FROM
[User],[Request]
WHERE
Request.UserId = [User].UserId
AND
Request.RequestId = Id
/*another selection*/
SELECT
ProductName
FROM
RequestProduct
WHERE
RequestId in
(
select id
from reqtable
)
It sounds like you actually just need to do a single selection:
SELECT
u.RequestId,
r.UserId,
rp.ProductName
FROM
[User] u
inner join
[Request] r
on
r.UserId = u.UserId
inner join
RequestProduct rp
on
rp.RequestId = r.RequestId
WHERE
r.RequestId = #Id
Generally, with SQL, you should decide what overall result you're trying to achieve, and then try to express it as a single statement - SQL Server's job (or any SQL product's) is to work out how best to construct the results. You shouldn't have to break down the problem into separate parts.
I don't know the etiquette here - this is a comment not a proposed answer but I want to make it easier for people to comment on my comment... downvote as appropriate... I don't want to just start a new question since I want the OP to see this.
You've got some alternatives but no one talked about why the first query didn't work or answered how to use the results of one query into another.
Why it didn't work: If the table "reqTable" existed and had a column named "id" at the time that your query was evaluated, SQL Server could have bound the name. You can use "eval" to put in sql that will be valid when it runs. For this problem that would be unjustifiably complex, but things like this must come up, I don't know if it's a regular tool in the toolbox of people who write a lot of stored procedures.
SQL Server 2005 and 2008 both have a feature called "CTE" you should read about that addresses the general question of "How do I use the results of one query in another query". They don't do anything subqueries absolutely can't do, but most of the time they are easier to write.
I have solved it. declare a table contains the result of first selection and use it in the second selection.
CREATE procedure [dbo].[ShowRequest] (#Id int)
AS
DECLARE #reqTable TABLE
(
ReqID int,
UserID int
)
INSERT INTO
#reqTable
SELECT
Request.RequestId AS 'ReqID',
Request.UserId
FROM
[User],[Request]
WHERE
Request.UserId = [User].UserId
AND
Request.RequestId = Id
/*another selection*/
SELECT
RequestProduct.ProductName
FROM
RequestProduct,#reqTable
WHERE
RequestProduct.RequestId = ReqID
Thanks for everyone who care about my question and spend his time to solve my problem
Locked. This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions.
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?
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
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.
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
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
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"
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
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())
In Management Studio, you can quickly get a comma-delimited list of columns for a table by :
In the Object Explorer, expand the nodes under a given table (so you will see folders for Columns, Keys, Constraints, Triggers etc.)
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.
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')
If you want to know the table structure, indexes and constraints:
sp_help 'TableName'
HashBytes() to return the MD2, MD4, MD5, SHA, or SHA1 hash of its input.
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
The spatial results tab can be used to create art.
enter link description here http://michaeljswart.com/wp-content/uploads/2010/02/venus.png
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.
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!
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'
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
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
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,
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)
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
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.
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
Return Date Only
Select Cast(Floor(Cast(Getdate() As Float))As Datetime)
or
Select DateAdd(Day, 0, DateDiff(Day, 0, Getdate()))
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
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
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 )
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"
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
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
Simple encryption with EncryptByKey