Suppose I have a table called "Languages" with two fields. One field is an Identity field that acts as the Primary Key. The second field is "LanguageName" which would naturally be "English", "Spanish", etc. What I want to do is put a constraint on the LanguageName field so that someone cannot enter the same name twice.
Is it better to create an Index --> Create UNIQUE and use:
a) Constraint?
b) Index with Ignore duplicate key checked?
Is there any benefit of one over the other for my purpose? Thanks.
I'm trying to weight the pros and cons of unique constraints and unique indexes. I understand that creating a unique constraint also creates an index. If that is the case, why not just use a unique index? Could someone give me an example of when you would want an unique constraint over an unique indexes
When I add a unique key constraint to column in SQL 6.5 why does it alsocreate an index. e.g. In the table subaccounts I added a unique keyconstraint for the column login and SQL creates an index with the nameUQ_SubAccounts_2__19 (UKC).Does this also mean that there is no need to create an index for thiscolumn?thxMansoor
I am creating a new SSIS package where there is a flat file (CSV) I am importing. Well, there will be an end-user using a web UI to initiate the import of the file. However, this flat file is generated from another company and then uploaded to our network.
This flat file has the potential to have duplicate rows that would have already been imported at a previous date. With the constraints in the table, we have guaranteed that there will not be duplicates added, but the SSIS package fails immediately upon attempting to insert a duplicate row - and the bulk update is rolled back.
What I need to be able to do is load all of the rows that are not duplicates into the table. I am guessing that with my current approach, this is not possible. I am using a Data Flow task that converts the data in the flat file and then performs a bulk copy to load the data into the table.
How can I either ignore duplicate rows, or otherwise gracefully handle this data import?
All,What's the difference between a unique contraint and unique?sementically, if you want a column contain unique values, it is acontraint. And an index is for searching/sort. The questions are:1. Does a unique constraint interally use unique index?2. If Yes to #1, I DO NOT need to create an index for search/sortpurpose, right?3. If Yes to #2, What's better?4. Also for Primary Key column, it is actually a special uniquecontraint. Not need to create index on PK column for searching/sorting,correct?5. Also for FK contraint, no need to create an index forsearching/sorting?ThanksJohn
When I create a unique constraint, SQL Server automatically creates an index on this constraint. So when I run the following...
ALTER TABLE PersonsProjects WITH NOCHECK ADD CONSTRAINT NoDupes UNIQUE NONCLUSTERED (PersonID, ProjectID)
...SQL Server will create a composite index on PersonsProjects called NoDupes on PersonIDand ProjectID. Thing is, I need this index to include a third column Status since most queries use this column in conjunction with PersonID and ProjectID. If there was no index on this table, I would have created it as follows:
CREATE UNIQUE INDEX NoDupes ON PersonsProjects (PersonID, ProjectID) INCLUDE (Status) WITH IGNORE_DUP_KEY
But this won't enforce the unique constraint on PersonID and ProjectID when performing inserts and updates. Is there any way of creating a unique constraint with an included column?
I would rather not have two indexes...
NoDupes: PersonID,ProjectID
New Index: PersonID,ProjectID INCLUDE Status
...so I'm trying to determine what other options that might be available...please advise.
We are on SQL 2014...we have a bunch of views in a database where we are trying to find the views which have more than 16 columns max for unique index/constraint...this is needed so we can convert them to indexed views...
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,
A UNIQUE INDEX must inherently impose a unique constraint and a UNIQUE CONSTRAINT is most likely implemented via a UNIQUE INDEX. So what is the difference? When you create in Enterprise Manager you must select one or the other.
What's the difference in the effect of the followings: CREATE UNIQUE NONCLUSTERED INDEX and ALTER TABLE dbo.titles ADD CONSTRAINT titleind UNIQUE NONCLUSTERED
I found there're two settings in Indexs/Keys dialog box of the management studio, Is Unique, and Type. The DDL statements above are generated by setting Is Unique to yes plus Type to Index, and just Type to Unique Key, respectively. What's the difference between them?
Hi everyone, I need urgent help to resolve this issue... As far as the performance goes which one is better.. Unique Index(col1, col2) OR Unique constraint(col1, col2) ? Unique constraint automatically adds a unique index and unique index takes care of uniqueness then whats the use of unique constraint ?
BOL says a unique constraint is preferred over a unique index. It also states that a unique constraint creates a unique index. What then is the difference between the two, and why is a constraint preferred over the index?
I am trying to create table with following SQL script:
Code Snippet
create table Projects( ID smallint identity (0, 1) constraint PK_Projects primary key, Name nvarchar (255) constraint NN_Prj_Name not null, Creator nvarchar (255), CreateDate datetime );
When I execute this script I get following error message:
Error source: SQL Server Compact ADO.NET Data Provider Error message: Named Constraint is not supported for this type of constraint. [ Constraint Name = NN_Prj_Name ]
I looked in the SQL Server Books Online and saw following:
CREATE TABLE (SQL Server Compact) ... < column_constraint > ::= [ CONSTRAINT constraint_name ] { [ NULL | NOT NULL ] | [ PRIMARY KEY | UNIQUE ] | REFERENCES ref_table [ ( ref_column ) ] [ ON DELETE { CASCADE | NO ACTION } ] [ ON UPDATE { CASCADE | NO ACTION } ]
As I understand according to documentation named constraints should be supported, however error message says opposite. I can rephrase SQL script by removing named constraint.
Code Snippet
create table Projects( ID smallint identity (0, 1) constraint PK_Projects primary key, Name nvarchar (255) not null, Creator nvarchar (255), CreateDate datetime ); This script executes correctly, however I want named constraints and this does not satisfy me.
please explain the differences btween this logical & phisicall operations that we can see therir graphical icons in execution plan tab in Management Studio
We are using SQL CE 3.5 on tablet PCs, that synchs with our host SQL 2005 Server using Microsoft Synchronization Services. On the tablets, when inserting a record, we get the following error: A duplicate value cannot be inserted into a unique index. [ Table name = refRegTitle,Constraint name = PK_refRegTitle But the only PK on this table is RegTitleID.
The table structure is: [RegTitleID] [int] IDENTITY(1,1) NOT NULL, [RegTitleNumber] [int] NOT NULL, [RegTitleDescription] [varchar](200) NOT NULL, [FacilityTypeID] [int] NOT NULL, [Active] [bit] NOT NULL,
The problem occurs when a Title Number is inserted and a record with that number already exists. There is no unique constraint on Title Number. Has anyone else experienced this?
I am using Full Text Index to index emails stored in BLOB column in a table. Index process parses stored emails, and, if there is one or more files attached to the email these documents get indexed too. In result when I'm querying the full text index for a word or phrase I am getting reference to the email containing the word of phrase if interest if the word was used in the email body OR if it was used in any document attached to the email.
How to distinguish in a Full Text query that the result came from an embedded document rather than from "main" document? Or if that's not possible how to disable indexing of embedded documents?
My goal is either to give a user an option if he or she wants to search emails (email bodies only) OR emails AND documents attached to them, or at least clearly indicate in the returned result the real source where the word or phrase has been found.
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.
My SSIS package is running very slow taking so much time to execute, One task is taking 2hr for inserting 100k records, i have disabled unused index still it is taking time.I am rebuilding/Refreshing indexes and stats once in month if i try to execute on daily basis will it improve my SSIS Package performance?
hello friends i have table1 and 200 coulumn of table1 :) i have 647.600 records. i entered my records to table1 with for step to code lines in one day :) i select category1 category2 and category3 with select code but i have just one index.. it is productnumber and it is primarykey..So my select code lines is so slow.. it is 7-9 second.. how can i select in 0.1 second ? Should i create index for category1 and category2 and category3 ? But i dont know create index.. My select code lines is below.. Could you learn me and show me index for it ?? or Could you learn me and show me fast Select code lines and index or etc ??? Also my search code line have a dangerous releated to attaching table1 with hackers :) cheersi send 3 value of treview1 node and childnode and child.childnode to below page.aspx :) Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Not Me.IsPostBack Then If Request("TextBox1") IsNot Nothing ThenTextBox1.Text = Request("TextBox1") End If If Request("TextBox2") IsNot Nothing ThenTextBox2.Text = Request("TextBox2") End If If Request("TextBox3") IsNot Nothing ThenTextBox3.Text = Request("TextBox3") End If End If Dim searchword As String If Request("TextBox3") = "" And Request("TextBox2") = "" Then searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "'" End If If Request("TextBox3") = "" Then searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "' and kategori1= '" & Request("TextBox2") & "'" End If If Request("TextBox3") <> "" And Request("TextBox2") <> "" And Request("TextBox1") <> "" Then searchword = "Select * from urunlistesi where kategori= '" & Request("TextBox1") & "' and kategori1= '" & Request("TextBox2") & "' and kategori2= '" & Request("TextBox3") & "'" End If SqlDataSource1.SelectCommand = searchword End Sub
I'm running a merge replication on a sql2k machine to 6 sql2k subscribers. Since a few day's only one of the merge agents fail's with the following error:
The merge process could not retrieve generation information at the 'Subscriber'. The index entry for row ID was not found in index ID 3, of table 357576312, in database 'PBB006'.
All DBCC CHECKDB command's return 0 errors :confused: I'm not sure if the table that's referred to in the message is on the distribution side or the subscribers side? A select * from sysobjects where id=357576312 gives different results on both sides . .
Hi everyone, When we create a clustered index firstly, and then is it advantageous to create another index which is nonclustered ?? In my opinion, yes it is. Because, since we use clustered index first, our rows are sorted and so while using nonclustered index on this data file, finding adress of the record on this sorted data is really easier than finding adress of the record on unsorted data, is not it ??
I 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?
Quick question about the primary purpose of Full Text Index vs. Clustered Index.
The Full Text Index has the purpose of being accessible outside of the database so users can query the tables and columns it needs while being linked to other databases and tables within the SQL Server instance. Is the Full Text Index similar to the global variable in programming where the scope lies outside of the tables and database itself?
I understand the clustered index is created for each table and most likely accessed within the user schema who have access to the database.
Is this correct?
I am kind of confused on why you would use full text index as opposed to clustered index.
One of the major syntax inside the SELECT statment is ..
WHERE FIELDA IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='A') AND WHERE FIELDB IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='B') AND WHERE FIELDC IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='C') AND WHERE FIELDD IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='D') AND WHERE FIELDE IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='E') AND WHERE FIELDF IN (SELECT PARAVALUE FROM PARATABLE WHERE SESSIONID = "XXXXX" AND PARATYPE='F')
(It's to compare the field content with some user input parameter inside a parameter table... )
I think properly is that the SELECT ... IN is causing much slowness in the sql statement. I have indexed FIELDA , FIELDB, FILEDC etc and those PARAVALUE and PARATYPE in the PARATABLE table. But perfromance is still slow and execution takes >20 seconds for 200000 rows of records.
Do any one know if still any chance to improvide the performance like this?
I'm trying to find whether there is a dmv or system view that can help me see the last time an index was rebuilt or created. Assuming I rebuilt an index using tsql commands (not a job with a history), is there a way to find out the last time that index was rebuilt?
SELECT a.AssetGuid, a.Name, a.LocationGuid FROM Asset a WHERE a.AssociationGuid IN ( SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
takes 30-60 seconds to run on my machine, due to a clustered index scan on our an index on asset [about half a million rows]. For this particular association less than 50 rows are returned.
expanding the inner select into a list of guids the query runs instantly:
SELECT a.AssetGuid, a.Name, a.LocationGuid FROM Asset a WHERE a.AssociationGuid IN ( '0F9C1654-9FAC-45FC-9997-5EBDAD21A4B4', '52C616C0-C4C5-45F4-B691-7FA83462CA34', 'C95A6669-D6D1-460A-BC2F-C0F6756A234D')
It runs instantly because of doing a clustered index seek [on the same index as the previous query] instead of a scan. The index in question IX_Asset_AssociationGuid is a nonclustered index on Asset.AssociationGuid.
The tables involved:
Asset, represents an asset. Primary key is AssetGuid, there is an index/FK on Asset.AssociationGuid. The asset table has 28 columns or so... Association, kind of like a place, associations exist in a tree where one association can contain any number of child associations. Each association has a ParentAssociationGuid pointing to its parent. Only leaf associations contain assets. AssociationDataAssociation, a table consisting of two columns, AssociationGuid, DataAssociationGuid. This is a table used to quickly find leaf associations [DataAssociationGuid] beneath a particular association [AssociationGuid]. In the above case the inner select () returns 3 rows.
I'd include .sqlplan files or screenshots, but I don't see a way to attach them.
I understand I can specify to use the index manually [and this also runs instantly], but for such a simple query it is peculiar it is necesscary. This is the query with the index specified manually:
SELECT a.AssetGuid, a.Name, a.LocationGuid FROM Asset a WITH (INDEX (IX_Asset_AssociationGuid)) WHERE a.AssociationGuid IN ( SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
To repeat/clarify my question, why might this not be doing a clustered index seek with the first query?
