Can I index a table in View ?

I create a view based on table. The table (say tblA) has an index on column
A.
When I do a sql query like "select .. from vMyView as MyView,tblB
where tblB.colA = MyView.A", will it use the index on tblA column A , or do
I
need to (and can I) create an index on the view ?
CREATE view vMyView()
select a,b,c...from tblA --> tblA.a is indexed
Thank you very much.Look up "Indexed views" in Books online.
Note - This feature is only supported in Enterprise/Developer editions.
Immy
"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:16F4C4B5-1006-4A73-9BDF-BF7C2CC36B80@.microsoft.com...
>I create a view based on table. The table (say tblA) has an index on column
>A.
> When I do a sql query like "select .. from vMyView as MyView,tblB
> where tblB.colA = MyView.A", will it use the index on tblA column A , or
> do I
> need to (and can I) create an index on the view ?
> CREATE view vMyView()
> select a,b,c...from tblA --> tblA.a is indexed
> Thank you very much.|||The base table index will be used, unless you create an indexed view. See
Books Online for details on how to create indexed views.
Indexed views basically allow you to index only a subset of data.
What exactly are you trying to achieve?
ML
http://milambda.blogspot.com/|||Not entirely true. From Books Online:
"
Indexed views can be created in any edition of SQL Server 2000. In SQL
Server 2000 Enterprise Edition, the query optimizer will automatically
consider the indexed view. To use an indexed view in all other editions, the
NOEXPAND hint must be used.
"
ML
http://milambda.blogspot.com/|||It will use the base table index if it is useful to do so (based on many
factors, like the selectivity of the index and your search argument)
You can index the view, provided it meets the strict requirements for doing
so. You can do it in any version, but as noted only in Enterprise Edition
will it use the index transparently, other versions require you to use the
NOEXPAND keyword so he text of the view isn't brought into the plan creation
(so you manually force it to treat the view as a table, more or less)
So the main reason I piped up and said basically the same things that were
said before is this. Do you know how to tell if an index is being used
using Management Studio / Query Analyzer? When it comes to predicting what
index may or may not be used, it generally behooves you to try it out.
There are menu items on both for displaying estimated plans, and then actual
plans that were used to execute the query. So execute the query and look at
the plan, and fiddle about with it for a while and you will get the hang of
when an index will be used.
----
Louis Davidson - http://spaces.msn.com/members/drsql/
SQL Server MVP
"Arguments are to be avoided: they are always vulgar and often convincing."
(Oscar Wilde)
"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:16F4C4B5-1006-4A73-9BDF-BF7C2CC36B80@.microsoft.com...
>I create a view based on table. The table (say tblA) has an index on column
>A.
> When I do a sql query like "select .. from vMyView as MyView,tblB
> where tblB.colA = MyView.A", will it use the index on tblA column A , or
> do I
> need to (and can I) create an index on the view ?
> CREATE view vMyView()
> select a,b,c...from tblA --> tblA.a is indexed
> Thank you very much.|||Thanks.
I guess I am worry that in a sql query like the following
"select .. from vMyView as MyView,tblB where tblB.colA = MyView.A", the
query will be slow if it does not use the base table index.
CREATE view vMyView()
select a,b,c...from tblA --> tblA.a is indexed
"ML" wrote:

> The base table index will be used, unless you create an indexed view. See
> Books Online for details on how to create indexed views.
> Indexed views basically allow you to index only a subset of data.
> What exactly are you trying to achieve?
>
> ML
> --
> http://milambda.blogspot.com/|||If you post more DDL (see here for details:
http://www.aspfaq.com/etiquette.asp?id=5006) , we can provide better help.
select .. from vMyView as MyView,tblB where tblB.colA = MyView.A
This may not be optimal. For one the old (deprecated) join syntax is used.
Compare the execution plan of your current query to the execution plan of
something like this:
select <columns>
from tblA
inner join tblB
on tblB.colA = tblA.colA
ML
http://milambda.blogspot.com/sql

Can I index a table in UDF ?

I create a UDF based on a table. The table (say tblA) has an index on column
A.
When I do a sql query like "select .. from dbo.udfMyProc() as MyProc,tblB
where tblB.colA = MyProc.A", will it use the index on tblA column A , or do
I
need to (and can I) create an index on the UDF ?
CREATE function dbo.udfMyProc()
returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
varchar(50), ...)
AS BEGIN
INSERT INTO @.myTable(a,b,c,d,e...)
select a,b,c...from tblA --> tblA.a is indexed
return
end
Thank you very much.That query will not use the index on "tblA" - you need to create one on the
temp table returned by the UDF. You cannot create a regular index on table
variables though (a CREATE INDEX statement), but you can use PRIMARY KEY and
UNIQUE constraints:
...
RETURNS @.tmp TABLE
(
somestring varchar(50) NOT NULL PRIMARY KEY
)
If the index can have non-unique records you can fake an index by adding an
identity column so that each record will be unique:
...
RETURNS @.tmp TABLE
(
somestring varchar(50) NOT NULL
, meaningless_column int NOT NULL IDENTITY(1,1)
, PRIMARY KEY (somestring, meaningless_column)
)
Make sure to make the IDENTITY column last in the PK/UNIQUE definition so
the index is still useful.
KH
"Paul fpvt2" wrote:

> I create a UDF based on a table. The table (say tblA) has an index on colu
mn A.
> When I do a sql query like "select .. from dbo.udfMyProc() as MyProc,tblB
> where tblB.colA = MyProc.A", will it use the index on tblA column A , or d
o I
> need to (and can I) create an index on the UDF ?
> CREATE function dbo.udfMyProc()
> returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
> varchar(50), ...)
> AS BEGIN
> INSERT INTO @.myTable(a,b,c,d,e...)
> select a,b,c...from tblA --> tblA.a is indexed
> return
> end
> Thank you very much.|||What do you mean by "use the index"? It will not copy the index onto
@.table, if that's what you mean. The only indexes you can create on a table
variable are via PRIMARY KEY or UNIQUE constraints... if you're talking
about ordering, that's a different conversation altogether...
"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:1BA572FB-C5DA-4528-BAB2-A484FA8837A8@.microsoft.com...
>I create a UDF based on a table. The table (say tblA) has an index on
>column A.
> When I do a sql query like "select .. from dbo.udfMyProc() as MyProc,tblB
> where tblB.colA = MyProc.A", will it use the index on tblA column A , or
> do I
> need to (and can I) create an index on the UDF ?
> CREATE function dbo.udfMyProc()
> returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
> varchar(50), ...)
> AS BEGIN
> INSERT INTO @.myTable(a,b,c,d,e...)
> select a,b,c...from tblA --> tblA.a is indexed
> return
> end
> Thank you very much.|||"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:1BA572FB-C5DA-4528-BAB2-A484FA8837A8@.microsoft.com...
>I create a UDF based on a table. The table (say tblA) has an index on
>column A.
> When I do a sql query like "select .. from dbo.udfMyProc() as MyProc,tblB
> where tblB.colA = MyProc.A", will it use the index on tblA column A , or
> do I
> need to (and can I) create an index on the UDF ?
> CREATE function dbo.udfMyProc()
> returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
> varchar(50), ...)
> AS BEGIN
> INSERT INTO @.myTable(a,b,c,d,e...)
> select a,b,c...from tblA --> tblA.a is indexed
> return
> end
> Thank you very much.
If your function truly consists of a single INSERT... SELECT statement then
you should turn it into an inline function rather than a multi-statement
one. That way your query against the function will be more likely to benefit
from an index on the base table. An example version of an inline function is
given below. This looks subtly different from what you posted but in terms
of the way the function works the difference is very significant.
CREATE function dbo.udfMyProc()
RETURNS TABLE
AS
RETURN (SELECT a,b,c...FROM tblA)
GO
BTW, if the function doesn't have any parameters then why use a function at
all? You could use a view for that.
Hope this helps.
David Portas
SQL Server MVP
--|||Thank you everybody for your replies.
I tried the view and it works a lot faster, I will use it instead.
But, I have a question about inline function. The example that you posted
looks the same with the UDF that I posted (CREATE function dbo.udfMyProc() )
What is the difference between UDF and inline function ?
Thanks a lot.
"David Portas" wrote:

> "Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
> news:1BA572FB-C5DA-4528-BAB2-A484FA8837A8@.microsoft.com...
> If your function truly consists of a single INSERT... SELECT statement the
n
> you should turn it into an inline function rather than a multi-statement
> one. That way your query against the function will be more likely to benef
it
> from an index on the base table. An example version of an inline function
is
> given below. This looks subtly different from what you posted but in terms
> of the way the function works the difference is very significant.
> CREATE function dbo.udfMyProc()
> RETURNS TABLE
> AS
> RETURN (SELECT a,b,c...FROM tblA)
> GO
> BTW, if the function doesn't have any parameters then why use a function a
t
> all? You could use a view for that.
> Hope this helps.
> --
> David Portas
> SQL Server MVP
> --
>
>|||One more question about inline function and views.
I understand that the ORDER BY clause is invalid in views and inline
functions.
If I need to use ORDER BY clause in my query inside the views or inline
function, Is there a way around it ?
Thanks.
"David Portas" wrote:

> "Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
> news:1BA572FB-C5DA-4528-BAB2-A484FA8837A8@.microsoft.com...
> If your function truly consists of a single INSERT... SELECT statement the
n
> you should turn it into an inline function rather than a multi-statement
> one. That way your query against the function will be more likely to benef
it
> from an index on the base table. An example version of an inline function
is
> given below. This looks subtly different from what you posted but in terms
> of the way the function works the difference is very significant.
> CREATE function dbo.udfMyProc()
> RETURNS TABLE
> AS
> RETURN (SELECT a,b,c...FROM tblA)
> GO
> BTW, if the function doesn't have any parameters then why use a function a
t
> all? You could use a view for that.
> Hope this helps.
> --
> David Portas
> SQL Server MVP
> --
>
>|||> What is the difference between UDF and inline function ?
there are two types of UDFs:
Inline. Consists of only one query. Think of it as a view or "macro".
Multi-statement. Here you define a table variable and populate that table va
riable, and when
function code exist at run-time the data is selected from the variable, All
that work is overhead.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
Blog: http://solidqualitylearning.com/blogs/tibor/
"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:B7BABDF8-B1A1-4735-BBFA-5A250B92B1F6@.microsoft.com...
> Thank you everybody for your replies.
> I tried the view and it works a lot faster, I will use it instead.
> But, I have a question about inline function. The example that you posted
> looks the same with the UDF that I posted (CREATE function dbo.udfMyProc()
)
> What is the difference between UDF and inline function ?
> Thanks a lot.
>
> "David Portas" wrote:
>|||Thanks.
Is the following UDF considered inline (because it only has 1 query: select
a,b,c...) ?
CREATE function dbo.udfMyProc()
returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
varchar(50), ...)
AS BEGIN
INSERT INTO @.myTable(a,b,c,d,e...)
select a,b,c...from tblA --> tblA.a is indexed
return
end
"Tibor Karaszi" wrote:

> there are two types of UDFs:
> Inline. Consists of only one query. Think of it as a view or "macro".
> Multi-statement. Here you define a table variable and populate that table
variable, and when
> function code exist at run-time the data is selected from the variable, Al
l that work is overhead.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
> news:B7BABDF8-B1A1-4735-BBFA-5A250B92B1F6@.microsoft.com...
>|||No, that is a multi-statement UDF. An Inline is:
CREATE FUNCTION f(...)
RETURNS TABLE
AS
RETURN (SELECT ...)
For above, SQL Server doesn't have to populate a table variable and then ret
urn the result. SQL
Server can, and will "inline" above query in the outer query, just like it d
oes with a view. Or
think of it as a macro, if you wish.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
Blog: http://solidqualitylearning.com/blogs/tibor/
"Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
news:D30F1F9A-E3D1-412A-B9D5-30A0F265B8C8@.microsoft.com...
> Thanks.
> Is the following UDF considered inline (because it only has 1 query: selec
t
> a,b,c...) ?
> CREATE function dbo.udfMyProc()
> returns @.myTable TABLE(a int, b bit, c varchar(50), d varchar(50), e
> varchar(50), ...)
> AS BEGIN
> INSERT INTO @.myTable(a,b,c,d,e...)
> select a,b,c...from tblA --> tblA.a is indexed
> return
> end
> "Tibor Karaszi" wrote:
>|||Thanks.
In the sample query that you posted, does it mean that you return a table
that is populated with the select statement ?
"Tibor Karaszi" wrote:

> No, that is a multi-statement UDF. An Inline is:
> CREATE FUNCTION f(...)
> RETURNS TABLE
> AS
> RETURN (SELECT ...)
> For above, SQL Server doesn't have to populate a table variable and then r
eturn the result. SQL
> Server can, and will "inline" above query in the outer query, just like it
does with a view. Or
> think of it as a macro, if you wish.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Paul fpvt2" <Paulfpvt2@.discussions.microsoft.com> wrote in message
> news:D30F1F9A-E3D1-412A-B9D5-30A0F265B8C8@.microsoft.com...
>