Use With(NOLOCK)
NOLOCK typically (depending on your DB
engine) means give me your data, and I don't care what state it is in, and
don't bother holding it still while you read from it. It is all at once faster,
less resource-intensive
Use NOLOCK on master tables and not
everywhere.
Using NoLock
may become dangerous sometimes,
so check the query exec plan when in doubt.
Select * from
ProductHierarchy WITH(NOLOCK)
Join On the InputParameter
This will reduce the operation size and
the disk read
Join on input parameter instead of
filtering in where condition.
As you can see here we have joined on setupid i.e the
input parameter instead of joining
on the setupid of
the other table and
then filtering in where condition.
SELECT * from trans.Promotion
P
inner join masters.Product
PP with(NOLOCK) on PP.SetupId=@local_SetupId
inner join masters.Customer
CC with(NOLOCK)
on
CC.SetupId=@local_SetupId
Instead Of
SELECT * from trans.Promotion
P
inner join masters.Product
PP with(NOLOCK) on PP.SetupId=P.SetupId
inner join masters.Customer
CC with(NOLOCK)
on
CC.SetupId=P.SetupId
Where PP.SetupId=@local_SetupId
Prevent the use of “Select *”
Causes
Indexing issues and Binding issues
Dont use "SELECT
*" in
a SQL
query
Insead use Select ProductId, ProductName from Products
Use EXISTS
To
check if any data exists in a particular table, use EXISTS instead of relying on Count its
more effective.
SELECT OrderId,AmendVersion
FROM
trans.OrdersWHERE
EXISTS
(SELECT
top 1 OrderId FROM
trans.OrderExtract WHERE
SetupId=1099)
Use Local Temp Tables (#TempTableName)
Prevent
using Global hash tables (##)
SELECT * into #TempProduct
FROM(SELECT
ProductId,LevelId,ProductCodeInterface,Name
from
Product where
SetupId=@local_SetupId
and
IsActive=1)
AS
TP
Use Local Variables to Store the FunctionCall return
Prevent
calling the string functions or date functions Over and over again, instead
store ‘em in local variables if you are going to reuse the
value.
Declare
@sampleString
varchar(max)
=
'nevermind the
promotions'
Declare @sizeOfString
int
set @sizeOfString=
len(@sampleString)
SELECT @sizeOfString
Use Try - Catch
BEGIN TRY
-- Logic / Query here
END TRY
BEGIN CATCH
-----------------------------------------------------------------------
DECLARE
@ErrMsg VARCHAR(255)
--
Error Message
,@ErrNo INT
--
Error Number
,@ErrSeverity
INT -- Error Severity
,@ErrProc VARCHAR(255)
--
Error Procedure
,@ErrLine INT
--
Error Line
SELECT
@ErrMsg = ERROR_MESSAGE()
,@ErrNo = ERROR_NUMBER()
,@ErrSeverity
=
17
,@ErrProc = ERROR_PROCEDURE()
,@ErrLine = ERROR_LINE()
RAISERROR (
@ErrMsg
,@ErrSeverity
,1
,@ErrNo
,@ErrLine
,@ErrProc
)
-----------------------------------------------------------------------
END CATCH
END
Use
SET
NOCOUNT
ON
Whenever we write any procedure and
execute it a message appears in message window that shows number of rows
affected with the statement written in the procedure.
When
SET NOCOUNT is ON, the count is not returned.
SET
NOCOUNT
ON
Select PromotionId from Promotion
Prevent Usage of DDL Statements
Do
not try to use DDL statements inside a stored procedure that will reduces the
chance to reuse the execution plan.
DDL statements like CREATE,ALTER,DROP,TRUNCATE etc.
Use Alias
If an alias is not present, the engine
must resolve which tables own the specified columns. A short alias is parsed
more quickly than a long table name or alias. If possible, reduce the alias to
a single letter
--Wrong Statement
SELECT PromotionId
,
P.VersionedPromotionId,
Name,
PIE.InvestmentTypeId
from
Promotion P
Inner join PromotionInvestment
PIE on
PIE.VersionedPromotionId=P.VersionedPromotionId
where P.Name='Blah'
--Correct Statement
SELECT P.PromotionId
,
P.VersionedPromotionId,
P.Name,
PIE.InvestmentTypeId
from
Promotion P
Inner join PromotionInvestment
PIE on
PIE.VersionedPromotionId=P.VersionedPromotionId
where P.Name='Blah'
Don't use UPDATE instead of CASE
Take this scenario, for instance: You're
inserting data into a temp table and need it to display a certain value if
another value exists. Maybe you're pulling from the Customer table and you want
anyone with more than $100,000 in orders to be labeled as "Preferred."
Thus, you insert the data into the table and run an UPDATE statement to set the
CustomerRank
column to "Preferred" for anyone who has more than $100,000 in
orders. The problem is that the UPDATE statement is logged, which means it has
to write twice for every single write to the table. The way around this, of
course, is to use an inline CASE statement in
the SQL query itself. This tests every row for the order amount condition and
sets the "Preferred" label before it's written to the table.
Avoid Functions on RHS
Dont use this
select *
from Promotion
where YEAR(StartDate)
=
2015
and
MONTH(StartDate)
=
6
Use this
Select *
From Promotion
Where StartDate
between
'6/1/2015'
and
'6/30/2015'
Specify optimizer hints in SELECT
most cases the query optimizer will pick
the appropriate index for a particular table based on statistics, sometimes it
is better to specify the index name in your SELECT query.
Do
not use this unless you know what you are doing.
SELECT *
FROM Promotion
WITH ( Index(IdxPromotionId))
WHERE Name =
'blah'
and Setupid=1099
Hope these tips will help you prevent and solve the timeout exception you face. If you want to add any please mention in the comments.
