Hi,
I created a composite index (lastname, firstname). I know the following
queries will use this index:
WHERE lastname = ...
WHERE lastname = ... AND firstname = ...
Also this won't use the index:
WHERE firstname = ...
But how about: WHERE firstname = .. AND lastname = ...
And why?
Thanks a lot,
Baihao
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
Want to check my thinking with you folks...
I have a table with a clustered composite index, consisting of 3 columns, which together form a unique key. For illustration, the columns are C1, C2 & C3.
Counts of distinct values for columns are C1 425, C2 300,000 & C3 4,000,000
C3 is effectively number of seconds since 01/01/1970.
The usage of the table is typically, insert a row, do something else, then update it.
Currently, the index columns are ordered C3,C1,C2. Fill factor of 90%.
My thinking is that this composite index is better ordered C1,C2,C3.
My reasoning is that having C3 as the leading column, biases all the inserts towards one side of the indexes underlying B-tree, causing page splits. Also, there'll be a bunch of "wasted" space across the tree, as the values going into C3 only ever get bigger (like an identity), so the space due to the fill factor in lower values never gets used.
Welcome your thoughts.
How do I improve a 3 column, composite clustered index on a large table when the developer insists there is no other way to achieve uniqueness? They say a uniqueindentifier column will not work.
View 5 Replies View RelatedI created composite clustered index key based on Gender and Salary columnÂ
The Query executed Successfully and <g class="gr_ gr_135 gr-alert gr_tiny gr_spell undefined ContextualSpelling multiReplace" data-gr-id="135" id="135">i</g>
got composite index key id Gender(-), Salary I <g class="gr_ gr_310 gr-alert gr_gramm undefined Grammar only-ins replaceWithoutSep" data-gr-id="310" id="310">want</g> know why Gender(-) display like this?
And Gender is <g class="gr_ gr_391 gr-alert gr_spell undefined ContextualSpelling ins-del multiReplace" data-gr-id="391" id="391">nvarchar</g>Â (20)Â
We are using partitioned unique indexes on partitioned tables. When the Unique Index is built, should the column the index is partitioned by be the top (leftmost) column in the index? While this violates cardinality, it makes sense (at least to me) that the first thing the query execution would do is figure out which partition(s) contain the result set, then filter from there.
What do you guys think? Is there any documentation on optimizing partitioned indexes?
Hi folks, i need an advise.
I've a gerand table customers_orders table with customer_id and order_id.
Whenever we have to find orders, for customer, this table is involved. Hey; i know u'll be angry y the heck this gerand exist but i've to blame the older dudes then.
Now this table has composite clustered index; CUSTOMER_ID+ORDER_ID.
The tables have grown over GB size; i see HASH INNER JOIN rather than MERGE for the GEREND and CUSTOMER table join.
Is it good to use composite clustered index; or should i clustered one the columns in the GEREND and other to normal index. What performance impact it could be.
Howdy!
When we create a composite key(col1,col2) clustered index is created in both col1 and col2.So how come "only one clustered can be created for a table" is justified?
View 8 Replies View RelatedHi everyone,
I have some problems on composite nonclustered indexes. I could not exatly understand their logic.
In my opininon, suppose that we have a table called Order and we create a composite nonclustered index on this table for OrderID column and OrderDate column. So I am using this query;
SELECT * FROM Order WHERE OrderID > 12 ORDER BY OrderDate
So in here, I think our first research is based on OrderID and ten after ordering our data pointer according to the OrderID and then our index is converted to an index which is based on OrderDate while performing ordering. So is this correct ??
Would you please explain this ?
Thanks
Is that possible on SQL Server 2000 and onwards?
View 1 Replies View RelatedWould it be OK to use varchar(5) instead of char(5) as the first field of acomposite clustered index?My gut tells me that varchar would be a bad idea, but I am not finding muchinformation on this topic on this when I Google it.Currently the field is Char(4), and there is a need to increase it to hold 5characters.TIA
View 2 Replies View RelatedI have a clustered index that consists of 3 int columns in this order: DateKey, LocationKey, ItemKey (there are many other columns in this data warehouse table such as quantities, prices, etc.).
Now I want to add a non-clustered index on just one of the other columns, say LocationKey, like this:
CREATE INDEX IX_test on TableName (LocationKey)
I understand that the clustered index keys will also be added as key columns to any NC indexes. So, in this case the NC index will also get the other two columns from the clustered index added as key columns. But, in what order will they be added?
Will the resulting index keys on this new NC index effectively be:
LocationKey, DateKey, ItemKey
OR
LocationKey, ItemKey, DateKey
Do the clustering keys get added to a NC index in the same order as they are defined in the clustered index?
Made an interesting discovery today - a column of data type Bit is not allowed to participate in composite key. Rather surprised.
I have a certain unique code that exhibits 2 unique states, which rendered the use of the boolean column, so the uniqueness goes <code>-1 and <code>-0. Is there any 'hack' so to speak to avoid using a Tinyint for the boolean column instead?
Hello,
I have a table which has a composite primary key consisting of four columns, one of them being a datetime called Day.
The nice thing afaik with this composite key is that it prevents duplicate entries in the table for any given day. But the problem is probably two-fold
1. multiple columns need to be used for joins and I think this might degrade performance?
2. in client applications such as asp.net these primary keys must be sent in the query string and the query string becomes long and a little bit unmanagable.
A possible solutions I'm thinking of is dropping the existing primary key and creating a new identity column and a composite unique index on the columns from the existing composite key.
I would like to have some tips, recommendations and alternatives for what I should do in this case.
I have several tables where I have used the command
distinct first_name, last_name, dob
to unduplicate.
I was wondering if I could create a new column in my table that combines the existing records for first_name, last_name and dob?
Hi All!I would like to have a composite PK on 3 columns, one of them is nullCREATE TABLE TableA (ColA int NOT NULL ,ColB int NOT NULL ,ColC char (3) NULL ,......)GOALTER TABLE TableA ADDCONSTRAINT TableA_PK PRIMARY KEY CLUSTERED(ColA,ColB,ColC)GOSQL Server does not allow having a composite PK with one nullable column:What is wrong to have values?1,100,NULL1,200,ABC1,200,ABD.....Code in C applies to Values in B and for some values in B the code does not exist.I can work out and define a special Code:NEV(not existing value), but in general I do not understand this restriction.Thanks
View 3 Replies View RelatedHi,
We got a problem.
supposing we have a table like this:
CREATE TABLE a (
aId int IDENTITY(1,1) NOT NULL,
aName string2 NOT NULL
)
go
ALTER TABLE a ADD
CONSTRAINT PK_a PRIMARY KEY CLUSTERED (aId)
go
insert into a values ('bank of abcde');
insert into a values ('bank of abcde');
...
... (20 times)
select top 5 * from a order by aName
Result is:
6Bank of abcde
5Bank of abcde
4Bank of abcde
3Bank of abcde
2Bank of abcde
select top 10 * from a order by aName
Result is:
11Bank of abcde
10Bank of abcde
9Bank of abcde
8Bank of abcde
7Bank of abcde
6Bank of abcde
5Bank of abcde
4Bank of abcde
3Bank of abcde
2Bank of abcde
According to this result, user see the first 5 records with id 6, 5, 4, 3, 2 in page 1, but when he tries to view page 2, he still see the records with id 6, 5, 4, 3, 2. This is not correct for users. :eek:
Of course we can add order by aid also, but there are tons of sqls like this, we can't update our application in one shot.
So I ask for your advice here, is there any settings can tell the db use default sort order when the order by column value are the same? Or is there any other solution to resolve this problem in one shot?
Hi,
We got a problem.
supposing we have a table like this:
CREATE TABLE a (
aId int IDENTITY(1,1) NOT NULL,
aName string2 NOT NULL
)
go
ALTER TABLE a ADD
CONSTRAINT PK_a PRIMARY KEY CLUSTERED (aId)
go
insert into a values ('bank of abcde');
insert into a values ('bank of abcde');
...
... (20 times)
select top 5 * from a order by aName
Result is:
6 Bank of abcde
5 Bank of abcde
4 Bank of abcde
3 Bank of abcde
2 Bank of abcde
select top 10 * from a order by aName
Result is:
11 Bank of abcde
10 Bank of abcde
9 Bank of abcde
8 Bank of abcde
7 Bank of abcde
6 Bank of abcde
5 Bank of abcde
4 Bank of abcde
3 Bank of abcde
2 Bank of abcde
According to this result, user see the first 5 records with id 6, 5, 4, 3, 2 in page 1, but when he tries to view page 2, he still see the records with id 6, 5, 4, 3, 2. This is not correct for users.
Of course we can add order by aid also, but there are tons of sqls like this, we can't update our application in one shot.
So I ask for your advice here, is there any settings can tell the db use default sort order when the order by column value are the same? Or is there any other solution to resolve this problem in one shot?
Dear All.
We had Teradata 4700 SMP. We have moved data from TD to MS_SQL SERVER 2003. records are 19.65 Millions.
table is >> Order_Dtl
Columns are:-
Client_ID varchar 10
Order_ID varchar 50
Order_Sub_ID decimal
.....
...
..
.
Pk is (ClientID+OrderId+OrderSubID)
Web Base application or PDA devices use to initiate the order from all over the country. The issue is this table is not Partioned but good HP with 30 GB RAM is installed. this is main table that receive 18,0000 hits or more. All brokers and users are using this table to see the status of their order.
The always search by OrderID, or ClientID or order_SubNo, or enter any two like (Client_ID+Order_Sub_ID) or any combination.
Query takes to much time when ever server receive more querys. some orther indexes are also created on the same table like (OrderDate, OrdCreate Date and Status)
My Question are:-
Q1. IF Person "A" query to DB on Client_ID, then what Index will use ? (If any one do Query on any two combination like Client_ID+Order_ID, So what index will be uesd.? How does MS-SQL SERVER deal with these kind of issues.?
Q2. If i create 3 more indexes on ClientID, ORderID and OrdersubID. will this improve the performance of query.if person "A" search record on orderNo so what index will be used. (Mind it their would be 3 seprate indexes for Each PK columns) and composite-Clustered index is also available.?
Q3. I want to check what indexes has been used? on what search?
Q4. How can i check what table was populated when, or last date of update (DML)?
My Limitation is i Dont Create a Partioned table. I dont have permission to do it.
In Teradata we had more than 4 tb record of CRM data with no issue. i am not new baby in db line but not expert in sql server 2003.
I am thank u to all who read or reply.
Arshad
Manager Database
Esoulconsultancy.com
(Teradata Master)
10g OCP
I want to make an index with the following columns, actually together they constitute the PK of the table so the index is created automatically.
The question is witch sort order is the best to have if I want to fetch all rows for one date and one resource? And why?
WHERE Resource = "Car 1" AND Date = "2013-03-03"
Resource, Date, Time
Or
Date, Time, Resource
Below is an example with tree resources, but in reality there can be a lot more and also years of dates.
Car 1, 2013-03-03, 10.00
Car 1, 2013-03-03, 11.00
Car 1, 2013-03-03, 12.00
Car 1, 2013-03-04, 10.00
[Code] ......
Is there a dynamic management view or system procedure which I can use to find out what columns are in an index, what columns are as an INCLUDE in the index and whether or not the column(s) are ascending or descending. This is excluding the utilities I already know about below:
sys.indexes
sys.index_columns
sp_helpindex
dm_db_index_physical_stats
dm_db_index_operational_stats
I only ask because it is a pain to look through the sys.indexes and sys.index_columns tables every time I want to know about what columns are in the index created. I also know that scripting the index would give me the information I need but there must be a better way.
Many Thanks
Does anyone have a general rule or guide on when to use this SQL 2000 option when creating indexes? I was thinking generally on nonclustered indexes where the column would be unique and incremental and usually filtered on by range and often used in the order by clause. Such as columns of datetime or integers datatypes. Thanks.
View 1 Replies View RelatedI have a table "Client" that has two columns: "ClientID" and "ProductID". I created on clustered index on ClientID and when I opened the table in the management studio, I saw the table was in the order of ClientID.
Then I added another non-clustered index on ProductID. When I open the table again, it is in the order of ProductID. Shouldn't the table always be in the order of clustered index? Non-clustered index should be a structure outside of the table itself? Did I do anything wrong?
Thanks for any hint.
Hi allI recently noticed when trying to optimise a major query of a chess websiteI am the webmaster of, that adding an order by for "gamenumber" which is aclustered index field as in for example "order by timeleft desc, gamenumberdesc" actually speeded up the queries and reduced sql server 2000 timeouts.I have an ASP error log and I am fairly sure that a dramatic reduction insql server timeouts is simply attributed to adding an extra seeminglyredundant order by field - which is the clustered index. Is this phenomenaat all possible or is it my imagination?!Other special attributes of the query includes the use of "Top" to obtain amaximum specified number of rows. Perhaps it is just the uniquecharacteristics of the query, but I would have thought that the less orderby fields would imply faster performance. Has anyone else noticed that aseemingly redundant order by column on for example the clustered indexcolumn, can actually help speed up queries?!Best wishesTryfon GavrielWebmasterwww.chessworld.net
View 4 Replies View Related
I have 2 columns in a table namely ColA and ColB.all DML operations are through views n every view has
Where clause i.e where ColA=€?€? with check option .
All most all my DML queries are using where clause on ColB
Where ColB=€?€?
Now my question is I have a clusted index on both ColA and ColB.in which order I have to create cluster index .
i.e ColA ASC,ColB ASC or ColB ASC,ColA ASC.
Is there any performance gain we can achieve with their order
Hi,
I want to ask a basic question, that is
IN WHAT ORDER A CLUSTERED INDEX SORT THE DATA IN THE COLUMN????
Somewhere in the MSDN library I read the following line:
"A clustered index physically sorts the table's contents in the order of the specified index columns"
But Sorting means it will be in ASCENDING ORDER (ASC) or It will be in DESCENDING ORDER (DESC)
So my question is lets suppose a column on which the cluistered index is defined and it contains character data liek abcd so in wht order it will sort the data alphabetically ASC or DESC
or
If the same above case with integer type of values, if column having integer values then in wht order the data in the table will be sorted.
??????
Thanks..!!!
Hi
I was going through the book by Kalen Delaney where she has mentioned the following paragpraph in Chapter 7 (Index Internals):
Many documents describing SQL Server indexes will tell you that the clustered index physically stores the data in sorted order. This can be misleading if you think of physical storage as the disk itself. If a clustered index had to keep the data on the actual disk in a particular order, it could be prohibitively expensive to make changes. If a page got too full and had to be split in two, all the data on all the succeeding pages would have to be moved down. Sorted order in a clustered index simply means that the data page chain is logically in order.
Then I read the book on SQL Server 2000 (on Perf Tuning) by Ken England. He says the clustered index stores data in physical order and any insert means moving the data physically. Also the same statement is echoed on the net by many articles.
What is the truth? How are really clustered index stored? What does physical order in the above statement really mean?
Regards
SanjaySi
Hi all,
I'm getting this "invalid descriptor index" exception while trying to fetch a record from the table.
The query is "select * from <tablename> where <columnname> = 'xyz'". The column name is correct and indeed a record with 'xyz' value exists. The record is getting fetched too...! But I'm having this particular error while trying to retrieve a couple of fields with rs.getString().
The order of columns in the table is same as the order in which I'm retrieving them. And I'm not facing any problem retrieving another field which has width of 200 characters.
I'll be very grateful indeed if someone can help me out of this particular problem...
Cheers, mates!
I upsized an access database with a key / index on ordernumber and linenumber.
However if I open the table in the Management Studio the records aren't ordered this way (same goes for select * from table) I get:
Ordernumber
Linenumber
200724001
37
200724004
3
200724006
33
200724001
3
200724011
19
200724014
5
200724006
37
200724011
19
200724006
28
Same goes for my crystal reports files, since the records aren't ordered by ordernumber / linenumber all my formulas go bezerk..
Am I wrong thinking the records should be ordered according to the prim. index?
Please help because I don't want to have to change all my 40+ reports to include an "ORDER BY"
Best regards,
Mike
In SQL 2012.A query that joins 2 table, with order by clause doesn't get sorted and the result set is not ordered. This happens when some of the columns in the where criteria are in a unique index which is the index that is used for the join between the 2 tables, and all the columns in the unique index are in the where criteria.In the query plan there is no component for sort.The work around was to drop the unique index, or change it to a non-unique index. Once this was done, the execution plan was changed to add the sort component (even when the index was changed to non-unique and the join was still using this index).
View 4 Replies View Related
Hi,
Please, What s the differnce between a column that s a primary key and a column that s a "key/index with Isunique=true"?
Thanks a lot.
We are running SQL Server 2014 Enterprise Edition (64-Bit) on Windows 2012 R2 Standard (64-Bit).
1. When to create indexes, before or after data is added? Please address Clustered and Non-Clustered Indexes.
2. To move indexes to it's own filegroup, is it best to create the NON-Clustered Indexes on the separate filegroup with code similar to the example below?
CREATE NONCLUSTERED INDEX IX_Employee_OrganizationLevel_OrganizationNode
ON HumanResources.Employee (OrganizationLevel, OrganizationNode)
WITH (DROP_EXISTING = ON)
ON TransactionsFG1;
GO
I have read the following links that states that if you create the Clustered Index on a separate filegroup, it would also move the base table to that particular filegroup. (So I take it that you ONLY can move NON-CLustered Indexes to a separate filegroup.)
Placing Indexes on Filegroups:
[URL]
By default, indexes are stored in the same filegroup as the base table on which the index is created. A nonpartitioned clustered index and the base table always reside in the same filegroup. However, you can do the following:
• Create nonclustered indexes on a filegroup other than the filegroup of the base table.
Move an Existing Index to a Different Filegroup:
[URL]
Limitations and Restrictions
• If a table has a clustered index, moving the clustered index to a new filegroup moves the table to that filegroup.
• You cannot move indexes created using a UNIQUE or PRIMARY KEY constraint using Management Studio. To move these indexes use the CREATE INDEX statement with the (DROP_EXISTING=ON) option in Transact-SQL.
I am really puzzled by an apparent difference between table index key column order and its statistics order. I was under understanding that index statistics mirror index definition. However, in my db 2470 index ordinal definitions match statistics definition but 66 do not. I also can reproduce such discrepancy in 2008 R2, 2012 and 2014.
As per definition,
stats_column_id
int
1-based ordinal within set of stats columns
This script duplicates this for me.
BEGIN TRAN
GO
use tempdb
GO
CREATE TABLE [dbo].[ItemProperties](
[itmID] [int] NOT NULL,
[cpID] [smallint] NOT NULL,
[ipuID] [tinyint] NOT NULL,
[Code] ....
The result I get is this:
object_id      stats_name                                    Â
stats_column_list
1525580473 PK_ItemProperties_itmID_ipuID_cpID itmID, cpID, ipuID,
and
object_id      index_name                                    Â
index_column_list
1525580473 PK_ItemProperties_itmID_ipuID_cpID itmID, ipuID, cpID,
Also a query I used to discover this in my db is:
WITH stat AS
(
SELECT
s.object_id
,s.name as stats_name
,(
SELECT
c.name + ', ' as [data()]
FROM sys.stats_columns as sc
[Code] .....
Hi,Would like to know the performance differenece between Multi-columnIndex vs Single Column Indexes. Let's say I have a table with col1,col2, col3 along with a primary key column and non-indexed columns.In queries, I will use col1, col2, and col3 together and some timesjust one or two of these three columns. My questions is, should Icreate one index contains col1, col2, and col3, or create 3 seperatedcolumns. I.e. each column has its own index. Any performancedifference?Thanks a lot.
View 1 Replies View Related