SQL Tip, Compiling Your SQL Without Running It to See If It Would Run

Let's say you have a big SQL script with a ton of code and you want to make sure it runs but you don't want to execute it because it updates tables, deletes data etc etc.
Take this simple example

SELECT GETDATE()
GO
SELECT 1/asasasas
GO


You can probably guess that the second statement is not valid, when you have a lot of code it is more difficult to spot these things.
Execeute the code above and you will get this


(1 row(s) affected)

Server: Msg 207, Level 16, State 1, Line 1
Invalid column name 'asasasas'.

SQL server has the SET NOEXEC statement. From BOL:

When SET NOEXEC is ON, Microsoft® SQL Server™ compiles each batch of
Transact-SQL statements but does not execute them. When SET NOEXEC is OFF, all
batches are executed after compilation.

The execution of statements in
SQL Server consists of two phases: compilation and execution. This setting is
useful for having SQL Server validate the syntax and object names in
Transact-SQL code when executing. It is also useful for debugging statements
that would usually be part of a larger batch of statements.

The setting
of SET NOEXEC is set at execute or run time and not at parse time.

So execute the code below

SET NOEXEC ON
GO

SELECT GETDATE()
GO
SELECT 1/asasasas
GO
SET NOEXEC OFF
GO



As you can see the output is the following:
Server: Msg 207, Level 16, State 1, Line 1
Invalid column name 'asasasas'.


You never see the getdate. Parsing that code will not throw an error and because of deferred name resolution you can fat-finger table names and it will parse without a problem.

Awesome Collection Of ASP.NET Hacks, Tips and Tricks

We added a bunch of ASP.NET Hacks, Tips and Tricks

we have the following categories
1 Applications
2 Caching
3 Controls
4 Database
5 Dates
6 Debugging
7 Email
8 Encryption
9 Files
10 Images
11 Javascript
12 Objects and Classes
13 Pages
14 Sessions
15 Strings
16 Validation
17 Visual Studio
18 Web

The URL to these hacks is here: http://wiki.lessthandot.com/index.php/ASP.NET_Hacks
Bookmark that URL because we will be adding more hacks, tips and tricks

Working On SQL Admin Hacks, Tips and Tricks

I haven't posted for a while because I have been working on SQL Admin Hacks, Tips and Tricks lately. it is still a work in progress but below is what is on the wiki currently. It is not yet categorized but we will do that once we get more of these hacks done. To see what it will look like when it is done take a look at the SQL Server Programming Hacks

Can you think of any admin stuff you would like to see? This is what we have right now

Find Primary Keys and Columns Used in SQL Server
Get The Domain Name Of Your SQL Server Machine With T-SQL
Grant Execute/SELECT Permissions For All User Defined Functions To A User
Grant Execute Permissions For All Stored Procedures To A User
Kill All Active Connections To A Database
SQL Server 2008: When Was The Server Last Started?
Check If Auto Update Statistics Is Enabled By Using DATABASEPROPERTY
Three Way To List All Databases On Your Server
Generate A List Of Object Types By Using OBJECTPROPERTY
How to find all the tables and views in a database
Find Out Server Roles For a SQL Server Login
Which Service Pack Is Installed On My SQL Server
Test SQL Server Login Permissions With SETUSER
Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection. SQL 2000
Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection. SQL 2005
Compare Tables With Tablediff
Find All Tables Without Triggers In SQL Server
Find All Tables With Triggers In SQL Server
Create Stored Procedures That Run At SQL Server Startup
Cycle The SQL Server Error Log
How to read sql server error messages
Use OBJECT_DEFINITION To Track SQL Server Stored Procedure Changes
SQL Compare Without The Price Tag
How To Get The Database Name For The Current User Process
How To Find Out Which Columns Have Defaults And What Those Default Values Are
Fixing Cannot add, update, or delete a job that originated from an MSX Server Error after renaming a server

Integer Math In SQL Server

What do you think the following query will return in SQL Server?

SELECT 3/2

If you said 1.5 then you are wrong! The correct answer is 1, this is because when doing division with 2 integers the result will also be an integer.
There are two things you can do
1 multiply one of the integers by 1.0
2 convert one of the integers to a decimal


Integer math is integer result
DECLARE @Val1 INT,@val2 INT
SELECT @Val1 =3, @val2 =2

SELECT @Val1/@Val2

Result 1

Convert explicit or implicit to get the correct answer
DECLARE @Val1 INT,@val2 INT
SELECT @Val1 =3, @val2 =2

--Implicit
SELECT @Val1/(@Val2*1.0)
--Explicit
SELECT CONVERT(DECIMAL(18,4),@Val1)/@Val2

Result 1.50000000000000

Return Null If A Value Is A Certain Value

You need to return NULL only if the value of your data is a certain value. How do you do this?
There are three different ways.

NULLIF
DECLARE @1 char(1)
SELECT @1 ='D'


SELECT NULLIF(@1,'D')


REPLACE
This should not really be used, I just added it here to demonstrate that you can in fact use it.

DECLARE @1 char(1)
SELECT @1 ='D'

SELECT REPLACE(@1,'D',NULL)


CASE
With case you can test for a range of values. You can test for example for values between A and D. If you reverse the logic then you also don't need to provide the ELSE part since it defaults to NULL anyway.

DECLARE @1 char(1)
SELECT @1 ='D'


SELECT CASE @1 WHEN 'D' THEN NULL ELSE @1 END

--No else needed
SELECT CASE WHEN @1 <> 'D' THEN @1 END

And this is how you test for a range.

--Null
DECLARE @1 char(1)
SELECT @1 ='D'

SELECT CASE WHEN @1 BETWEEN 'A' AND 'D' THEN NULL ELSE @1 END

--E
DECLARE @1 char(1)
SELECT @1 ='E'

SELECT CASE WHEN @1 BETWEEN 'A' AND 'D' THEN NULL ELSE @1 END

Sort Values Ascending But NULLS Last

This is a frequent request in newsgroups and fora. People want to sort the column in ascending order but don't want the NULLS at the beginning.
Oracle has this syntax: ORDER BY ColumnName NULLS LAST;
SQL Server does not have this. But there are 2 ways to do this. The first one is by using case and the second one by using COALESCE and the maximum value for the data type in the order by clause.

The 2 approaches with a datetime data type

DECLARE @Temp table(Col datetime)
INSERT INTO @Temp VALUES(getdate())
INSERT INTO @Temp VALUES('2007-10-19 09:54:03.730')
INSERT INTO @Temp VALUES('2006-10-19 09:54:03.730')
INSERT INTO @Temp VALUES('2005-10-19 09:54:03.730')
INSERT INTO @Temp VALUES('2006-10-19 09:54:03.730')
INSERT INTO @Temp VALUES('2004-10-19 09:54:03.730')
INSERT INTO @Temp VALUES(NULL)
INSERT INTO @Temp VALUES(NULL)

SELECT *
FROM @Temp
ORDER BY COALESCE(Col,'9999-12-31 23:59:59.997')

SELECT *
FROM @Temp
ORDER BY CASE WHEN Col Is NULL Then 1 Else 0 End, Col

The 2 approaches with an integer data type

DECLARE @Temp table(Col int)
INSERT INTO @Temp VALUES(1)
INSERT INTO @Temp VALUES(555)
INSERT INTO @Temp VALUES(444)
INSERT INTO @Temp VALUES(333)
INSERT INTO @Temp VALUES(5656565)
INSERT INTO @Temp VALUES(3)
INSERT INTO @Temp VALUES(NULL)
INSERT INTO @Temp VALUES(NULL)

SELECT *
FROM @Temp
ORDER BY COALESCE(Col,'2147483647')

SELECT *
FROM @Temp
ORDER BY CASE WHEN Col Is NULL Then 1 Else 0 End, Col

SQL Gotcha: Do you know what data type is used when running ad-hoc queries?

This is for SQL Server 2000 only, SQL Server 2005 is a lot smarter which is another reason to upgrade.
When running the following query you probably already know that 2 is converted to an int datatype


SELECT *
FROM Table
WHERE ID =2

What about the value 2222222222? Do you think since it can't fit into an int that it will be a bigint? Let's test that out.
First create this table.

CREATE TABLE TestAdHoc (id bigint primary key)

INSERT INTO TestAdHoc
SELECT 1 UNION
SELECT 2433253453453466666 UNION
SELECT 2 UNION
SELECT 3 UNION
SELECT 4 UNION
SELECT 5 UNION
SELECT 6


Now let's run these 2 queries which return the same data

SELECT *
FROM TestAdHoc
WHERE ID =2433253453453466666



SELECT *
FROM TestAdHoc
WHERE ID =CONVERT(bigint,2433253453453466666)

Now run the following SET statement and run the 2 queries again

SET SHOWPLAN_TEXT ON

SELECT *
FROM TestAdHoc
WHERE ID =2433253453453466666


SELECT *
FROM TestAdHoc
WHERE ID =CONVERT(bigint,2433253453453466666)

And what do we see?

First Query
--Nested Loops(Inner Join, OUTER REFERENCES:([Expr1002], [Expr1003], [Expr1004]))
--Compute Scalar(DEFINE:([Expr1002]=Convert([@1])-1,
[Expr1003]=Convert([@1])+1, [Expr1004]=If (Convert([@1])-1=NULL)
then 0 else 6If (Convert([@1])+1=NULL) then 0 else 10))
--Constant Scan
--Clustered Index Seek(OBJECT:([Blog].[dbo].[TestAdHoc].[PK__TestAdHoc__2818EA29]),
SEEK:([TestAdHoc].[id] > [Expr1002] AND [TestAdHoc].[id] < [Expr1003]), WHERE:(Convert([TestAdHoc].[id])=[@1]) ORDERED FORWARD)

Second Query
--Clustered Index Seek(OBJECT:([Blog].[dbo].[TestAdHoc].[PK__TestAdHoc__2818EA29]),
SEEK:([TestAdHoc].[id]=2433253453453466666) ORDERED FORWARD)


The first query has a much different execution plan than the second query. The first execution plan has a lot more than the second execution plan and will be a little slower.

So how do you know what dataype the value is converted to? Here is a simple SQL query which I first saw on Louis Davidson's blog. Just run this query.

SELECT CAST(SQL_VARIANT_PROPERTY(2433253453453466666,'BaseType') AS varchar(20)) + '(' +
CAST(SQL_VARIANT_PROPERTY(2433253453453466666,'Precision') AS varchar(10)) + ',' +
CAST(SQL_VARIANT_PROPERTY(2433253453453466666,'Scale') AS varchar(10)) + ')'

So the output is this numeric(19,0). So instead of a bigint SQL Server converts the value to a numeric data type.
Here is another query which demonstrates the different datatypes used.


SELECT CAST(SQL_VARIANT_PROPERTY(2,'BaseType') AS varchar(20))
UNION ALL
SELECT CAST(SQL_VARIANT_PROPERTY(222222222,'BaseType') AS varchar(20))
UNION ALL
SELECT CAST(SQL_VARIANT_PROPERTY(2222222222,'BaseType') AS varchar(20))


So when running ad-hoc queries it is always a good practice to use parameters or inline convert statements.

Cannot resolve collation conflict for equal to operation.

You set up your linked server, you write a query which joins two tables, you execute the query and the error message is this
Cannot resolve collation conflict for equal to operation


What does this mean? This mean that the collation on the two tables is different

Let's look at an example. Le's create two tables, onme with Traditional_Spanish_CI_AI collation and one with the default. The default collation for me is SQL_Latin1_General_CP1_CI_AS.


CREATE TABLE #Foo (SomeCol varchar(50) COLLATE Traditional_Spanish_CI_AI)
CREATE TABLE #Foo2 (SomeCol varchar(50))


INSERT #Foo VALUES ('AAA')
INSERT #Foo VALUES ('BBB')
INSERT #Foo VALUES ('CCC')
INSERT #Foo VALUES ('DDD')

INSERT #Foo2 VALUES ('AAA')
INSERT #Foo2 VALUES ('BBB')
INSERT #Foo2 VALUES ('CCC')
INSERT #Foo2 VALUES ('DDD')

Now run this query and you will get the error message

SELECT * FROM #Foo F1
JOIN #Foo2 f2 ON f1.SomeCol = f2.SomeCol


Server: Msg 446, Level 16, State 9, Line 1
Cannot resolve collation conflict for equal to operation.

Now add COLLATE Traditional_Spanish_CI_AI to #Foo2 SomeCol

SELECT * FROM #Foo F1
JOIN #Foo2 f2 ON f1.SomeCol = f2.SomeCol COLLATE Traditional_Spanish_CI_AI

That works, if you add COLLATE SQL_Latin1_General_CP1_CI_AS to #Foo SomeCol that will work also


SELECT * FROM #Foo F1
JOIN #Foo2 f2 ON f1.SomeCol COLLATE SQL_Latin1_General_CP1_CI_AS = f2.SomeCol


If you want to know what these collations mean then run the following query (yes that is not a typo it is indeed ::).

SELECT *
FROM ::fn_helpcollations()
WHERE name in('SQL_Latin1_General_CP1_CI_AS','Traditional_Spanish_CI_AI')

Traditional_Spanish_CI_AI
Traditional-Spanish,
case-insensitive,
accent-insensitive,
kanatype-insensitive,
width-insensitive

SQL_Latin1_General_CP1_CI_AS
Latin1-General,
case-insensitive,
accent-sensitive,
kanatype-insensitive,
width-insensitive for Unicode Data,
SQL Server Sort Order 52 on Code Page 1252 for non-Unicode Data

Make Your Case Sensitive Searches 1000 Times Faster

I had an case sensitive update query that ran in about 9 minutes. Since it was a case sensitive query it did an index scan not an index seek.
Once I modified my WHERE clause the update took a little less than 3 seconds

Let's get started and see what I did

First create this table

CREATE TABLE #CaseSensitiveSearchTemp (Val CHAR(1))

INSERT #CaseSensitiveSearchTemp VALUES('A')
INSERT #CaseSensitiveSearchTemp VALUES('B')
INSERT #CaseSensitiveSearchTemp VALUES('C')
INSERT #CaseSensitiveSearchTemp VALUES('D')
INSERT #CaseSensitiveSearchTemp VALUES('E')
INSERT #CaseSensitiveSearchTemp VALUES('F')
INSERT #CaseSensitiveSearchTemp VALUES('G')
INSERT #CaseSensitiveSearchTemp VALUES('H')

Now we will insert some lowercase characters

INSERT #CaseSensitiveSearchTemp
SELECT LOWER(Val) FROM #CaseSensitiveSearchTemp

Now we will create our real table which will have 65536 rows

CREATE TABLE CaseSensitiveSearch (Val VARCHAR(50))

We will do a couple of cross joins to generate the data for our queries

INSERT CaseSensitiveSearch
SELECT t1.val + t2.val + t3.val + t4.val
FROM #CaseSensitiveSearchTemp t1
CROSS JOIN #CaseSensitiveSearchTemp t2
CROSS JOIN #CaseSensitiveSearchTemp t3
CROSS JOIN #CaseSensitiveSearchTemp t4


This should give you 65536 rows

SELECT * FROM CaseSensitiveSearch


Create an index on the table

CREATE INDEX IX_SearchVal ON CaseSensitiveSearch(Val)


This is how you do a case sensitive search

SELECT * FROM CaseSensitiveSearch
WHERE Val = 'ABCD' COLLATE SQL_Latin1_General_CP1_CS_AS



Now hit CRLK + K (SQL Server 2000) or CRLK + M(SQL Server 2005)

run these 2 queries in one batch by highlighting them both and hitting F5

SELECT * FROM CaseSensitiveSearch
WHERE Val = 'ABCD' COLLATE SQL_Latin1_General_CP1_CS_AS

SELECT * FROM CaseSensitiveSearch
WHERE Val = 'ABCD' COLLATE SQL_Latin1_General_CP1_CS_AS
AND Val LIKE 'ABCD'

Look at the execution plan, I get 98.71% for the first query and 1.29% for the second query. Just by adding the AND condition SQL server is able to do an index seek and run the query many times faster




Now try it with a lowercase a

SELECT * FROM CaseSensitiveSearch
WHERE Val = 'aBCD' COLLATE SQL_Latin1_General_CP1_CS_AS

SELECT * FROM CaseSensitiveSearch
WHERE Val = 'aBCD' COLLATE SQL_Latin1_General_CP1_CS_AS
AND Val LIKE 'aBCD'


You see it all works without a problem, the correct result is returned

Three Ways To Return All Rows That Contain Uppercase Characters Only

How do you select all the rows that contain uppercase characters only? There sre three ways to do this
1 Compare with BINARY_CHECKSUM
2 Use COLLATE
3 Cast to varbinary

Let's first create the table and also some test data

CREATE TABLE #tmp ( x VARCHAR(10) NOT NULL )


INSERT INTO #tmp
SELECT 'Word' UNION ALL
SELECT 'WORD' UNION ALL
SELECT 'ABC' UNION ALL
SELECT 'AbC' UNION ALL
SELECT 'ZxZ' UNION ALL
SELECT 'ZZZ' UNION ALL
SELECT 'word'


if we want only the uppercase columns then this is supposed to be our output

WORD
ABC
ZZZ

Let's get started, first up is BINARY_CHECKSUM

SELECT x
FROM #TMP
WHERE BINARY_CHECKSUM(x) = BINARY_CHECKSUM(UPPER(x))


Second is COLLATE

SELECT x
FROM #TMP
WHERE x = UPPER(x) COLLATE SQL_Latin1_General_CP1_CS_AS

Third is Cast to varbinary

SELECT x
FROM #TMP
WHERE CAST(x AS VARBINARY(10)) = CAST(UPPER(x) AS VARBINARY(10))


Of course if you database is already case sensitive you can just do the following

SELECT x
FROM #TMP
WHERE UPPER(x) = x

That will work, how do you find out what collation was used when your database was created? You can use DATABASEPROPERTYEX for that. I use the model DB here because when you create a new DB by default it inherits all the properties from the model DB.
When I run this
SELECT DATABASEPROPERTYEX( 'model' , 'collation' )

I get this as output: SQL_Latin1_General_CP1_CI_AS


What does all that junk mean? Well let's run the following function (yes those are 2 colons ::)
SELECT *
FROM ::fn_helpcollations ()
WHERE NAME ='SQL_Latin1_General_CP1_CI_AS'

The description column contains this info


Latin1-General, case-insensitive, accent-sensitive,
kanatype-insensitive, width-insensitive for Unicode Data,
SQL Server Sort Order 52 on Code Page 1252 for non-Unicode Data

You can read some more info about Selecting a SQL Collation here: http://msdn2.microsoft.com/en-us/library/aa176552(SQL.80).aspx

How To Get The Database Name For The Current User Process

This question pops up frequent enough so here are 4 ways to return the database name for the current user process

First up is the fastest method. this will run on SQL Server 200 and 2005

SELECT DB_NAME()


Next up is getting the name by joining the sys.dm_exec_requests dmv and sys.sysdatabases. this runs on SQL Server 2005 only

SELECT s.name
FROM sys.dm_exec_requests d
JOIN sys.sysdatabases s on d.database_id = s.dbid
WHERE session_id = @@SPID

Here is something similar, this also runs only on SQL Server 2005

SELECT name
FROM sys.sysdatabases
WHERE dbid = DB_ID()


And we end with something that runs on both SQL Server 2005 and 2000
SELECT name
FROM master..sysdatabases
WHERE dbid = DB_ID()


But like I said before you should always use DB_NAME()

ASP.NET Library Site Launched

A friend of mine has started the ASP.NET Library site. The idea of this site is to provide ASP.NET articles, code and tips for professional ASP.NET developers. The site right now offers Resources, Articles and a Code Bank. Under Code Bank you can find the following:
Applications
Controls
Database
Email
HTML

So go ahead and check it out: http://aspnetlibrary.com/

Use A Combination OF NULLIF and COALESCE TO Display A Custom Value

Let's you inherit a table with a column that can contain blanks, empty strings or NULL values. I am saying inherit because surely you would have a constraint on the column that wouldn't allow those values to begin with right? For all the values that are '',' ' or NULL you want to display 'N/A'.
What is the best way to do this? You can Use CASE and test for the values or you can use COALESCE with NULLIF which is much shorter. A lot of people don't know that you can stack these functions so that it makes your life so much easier.
Let's get started

CREATE TABLE Blah (SomeCol VARCHAR(33))

INSERT Blah VALUES(NULL)
INSERT Blah VALUES('')
INSERT Blah VALUES(' ')
INSERT Blah VALUES('A')
INSERT Blah VALUES('B B')

--Using COALESCE and NULLIF
SELECT COALESCE(NULLIF(RTRIM(SomeCol),' '),'N/A')
FROM Blah


--Using CASE
SELECT CASE WHEN RTRIM(SomeCol) = '' THEN 'N/A'
WHEN RTRIM(SomeCol) IS NULL THEN 'N/A'
ELSE SomeCol END SomeCol
FROM Blah


Output for both queries
-----------------------
N/A
N/A
N/A
A
B B

How To Restart A Remote Computer

Sometimes you have to login to your work PC from home over the VPN and after a while for some reason or another you want to restart your PC. How can you do that? You can't use the start menu because only the log off button is displayed
Well one way is to open a command window and executing shutdown -r
That will restart your computer

Here is the basic usage of the shutdown command

Usage: shutdown [-i -l -s -r -a] [-f] [-m \\computername] [-t xx] [-c "comment"] [-d up:xx:yy]

No args Display this message (same as -?)
-i Display GUI interface, must be the first option
-l Log off (cannot be used with -m option)
-s Shutdown the computer
-r Shutdown and restart the computer
-a Abort a system shutdown
-m \\computername Remote computer to shutdown/restart/abort
-t xx Set timeout for shutdown to xx seconds
-c "comment" Shutdown comment (maximum of 127 characters)
-f Forces running applications to close without warning
-d [u][p]:xx:yy The reason code for the shutdown
u is the user code
p is a planned shutdown code
xx is the major reason code (positive integer less than 256)
yy is the minor reason code (positive integer less than 65536)

Fun With SQL Server Update Triggers

Below is some code that will show how to test for updated field values in an update trigger. As you can see the IF UPDATE (field) is true even when the values don’t change. Another thing to keep in mind is that if a value changes from NULL to something else and vice-versa, and you are comparing deleted and inserted tables without using COALESCE or ISNULL it won’t return those rows. Run the code below to see what I mean


CREATE TABLE TestTrigger (TestID INT identity,
name VARCHAR(20),
value DECIMAL(12,2) ,
CONSTRAINT chkPositiveValue CHECK (value > 0.00) )


INSERT INTO TestTrigger
SELECT 'SQL',500.23


CREATE TRIGGER trTest
ON TestTrigger
FOR UPDATE
AS

IF @@ROWCOUNT =0
RETURN

IF UPDATE(value)
BEGIN
SELECT '1', * FROM deleted d JOIN inserted i ON d.testid =i.testid
SELECT '2',* FROM deleted d JOIN inserted i ON d.testid =i.testid
AND i.value <> d.value
SELECT '3',* FROM deleted d JOIN inserted i ON d.testid =i.testid
AND COALESCE(i.value,-1) <> COALESCE(d.value,-1)
END
GO

--Let's update the value to 100
UPDATE TestTrigger SET value = 100 WHERE testid =1
--we get back all 3 rows


--Let's run the same statement
UPDATE TestTrigger SET value = 100 WHERE testid =1
--we get back the first row


--Let's really update
UPDATE TestTrigger SET value = 200 WHERE testid =1
--we get back all 3 rows

--Let's update with NULL
UPDATE TestTrigger SET value =NULL WHERE testid =1
--we get back rows 1 and 3, row 2 is not returned because it can't compare it

--Let's update with NULL again
UPDATE TestTrigger SET value =NULL WHERE testid =1
--we get back row 1

--Let's update with 300
UPDATE TestTrigger SET value =300 WHERE testid =1
--we get back rows 1 and 3, row 2 doesn't return because it can't compare NULL to 300

--Let's update with 500
UPDATE TestTrigger SET value =500 WHERE testid =1
--we get back all 3 rows