Sql-server – sql server set implicit_transactions off and other options

sql server

I am still learning sql server somewhat and recently came across a select query in a stored procedure which was causing a very slow fill of a dataset in c#. At first I thought this was to do with .NET but then found a suggestion to put in the stored procedure:

set implicit_transactions off

this seems to cure it but I would like to know why also I have seen other options such as:

set nocount off
set arithabort on
set concat_null_yields_null on
set ansi_nulls on
set cursor_close_on_commit off
set ansi_null_dflt_on on
set ansi_padding on
set ansi_warnings on
set quoted_identifier on

Does anyone know where to find good info on what each of these does and what is safe to use when I have stored procedures setup just to query of data for viewing.

I should note just to stop the usual use/don't use stored procedures debate these queries are complex select statements used on multiple programs in multiple languages it is the best place for them.

Edit: Got my answer didn't end up fully reviewing all the options but did find

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

Sped up the complex queries dramatically, I am not worried about the dirty read in this instance.

Best Answer

This is the page out of SQL Server Books Online (BOL) that you want. It explains all the SET statements that can be used in a session. http://msdn.microsoft.com/en-us/library/ms190356.aspx

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to return only the Date from a SQL Server DateTime datatype

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date))

for example

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE()))

gives me

2008-09-22 00:00:00.000

Pros:

No varchar<->datetime conversions required
No need to think about locale

Best Answer

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Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to return only the Date from a SQL Server DateTime datatype

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