Uniqueness Constraint Question
Apr 24, 2008
Hello,
My company is upgrading one of our products; this involves some data migration and a question about existing indexes with uniqueness constraints has been raised. Here is the issue:
We have a database table with two particular columns that that we index with a uniqueness constraint. My question is: is the uniqueness constraint case sensitive?
For instance, if I have a database that is using a collation of SQL_Latin1_General_CP1_CS_AS. (case sensitive) and I insert data in these two columns as follows:
test
col2test
Test
col2test
would this uniqueness constraint be violated even though I'm using a case sensitive collation? I've done tests on this issue and I can't seem to insert this 2nd column; I'm just wanting to be certain that this is the case 100% of the time.
Thanks for your assistance,
Aaron
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Jul 5, 2000
Hi,
Can anyone tell me the order in which uniqueness constraints on indexes are enforced vs. when triggers are executed ? I have a unique constraint on an index and a trigger on the column on which the same index has been created. When a row is inserted, the trigger checks if the value for that column already exists in the table - if not, it inserts the row as is, else it gets the max() val of the column (based on another key column) and increments it by one, then does the insert. Creating an index across the two works fine, but if I set the Unique Values property for the index, subsequent inserts bomb out - yet there aren't any duplicates in the final table, as the trigger ensures this. Anyone got any ideas on this? My deduction is that the uniqueness constraint gets enforced before the trigger gets executed, but at the same time this *seems* illogical, as the row has not been inserted into the table at the point where the trigger is executed.
Regards,
Jon Reade.
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Aug 16, 2012
I"m trying to use a BULK INSERT command to insert data into a table from a file. There is a UNIQUE Index that is being violated and the BULK INSERT fails.
I do not want to drop or disable the index, however, i also do not want to load 'duplicate' records so i keep the CHECK_CONSTRAINTS parameter.
Is there a way to have the duplicate records outputed to the ERRORFILE ?
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Sep 21, 2000
When I select a fieldname in a db as a primary key this will keep the uniqueness of that fieldname, but how is that work when I select 2 fieldnames (in Enterprise Manager) and click on the Key it will mark them as my primary key, but I can insert duplicates values in either fieldname.
Can someone explain this to me.
Thanks
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Aug 7, 2007
hi
am new to sql...i need to write a query ..it is like two teams can play more than 1 game but on different dates..
so if i create the table like this
Create Table Games( TeamName1 char(30),
2 numGoals1 int,
3 TeamName2 char(30),
4 numGoals2 int,
5 play_date char(10),
6 primary key(TeamName1,TeamName2,play_date),
7 Check(TeamName1!=TeamName2)
8 );
this violates the constraint if i give the two teams on the same date..how to give the condition such that it checks for the violation of condition if the team names are interchanged.. for eg
if i give the values as
Insert Into Games values('chelsea',1,'arsenal',2,'17-1-2000');
and
Insert Into Games values('arsenal',1,'chelsea',2,'17-1-2000');
the above should violate the constraint ..how to do it
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Jan 22, 2014
OK - maybe my Google-fu is off today but I'm trying to find out if using a sequence table will provide values that are as unique as the GUID is supposed to be.The reason is that I'm building a DW from the ground up (they won't let me expense my booze which I think is grossly unfair ) and rather than using GUID it ~seems~ like a sequence table would give better results. My concern is that the values won't be unique across tables.
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Jul 20, 2005
Hi,First of all my apologies if you have seen this mail already but I amre-sending as there were some initial problems.This query is related to defining indexes to be unique or not andconsequences thereof.Some documented facts that I am aware of include1. Defining uniqueness allows optimiser to create optimal plans egselect based on keys in such an index allows the optimiser to determineat most only one row will be returned2. Defining uniqueness ensures that rule (business/Primary key) isenforced, regradless of how the data is entered.We have many cases where non unique indexes are defined. The approach todate has been that even though we are aware of some of the benefitsoffered by defining uniqueness , we have chosen not to add keys to nonunique indexes such that they become unique. The primary reason for thiswas that we did not want to make the keys comprising the indexesunnecessarily large and therefore ensuing consequences when DMLstatements are performed.However, I have concerns that having highly duplicate indexes can haveperformance impacts , including deadlocking. I am also aware Sybase usedto store duplicate values in overflow pages and therefore there wereperformance consequences. Could SQL 2000 have the same behaviour ?Thanking you in advancePuvendran*** Sent via Developersdex http://www.developersdex.com ***Don't just participate in USENET...get rewarded for it!
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Jun 17, 2008
So, I have this idea of a database design I was hoping to get some input on.
I usually go through the process of creating a separate column for identity, like an auto-increment integer which serves as a context specific ID that easily can be passed around. However one of the short-comings I've come to realize is that the integer is just that, unique to the context and requires context information to make sense.
I'm pounding the idea of creating a separate table whose sole purpose is to provide global (database wide) unique IDs. As such each row in a table can still have an ID but instead of being tied to a specific context it will always make sense within the application. A foreign key constraint can ensure that and a relation.
Now, with a global ID which I can create FKs to, I don't have to create a separate table for relations between entities and can have relations through these global IDs and I think that's a good thing because if there are many relations between many entities they don't have to be defined more than once. There is also a single "hub" where all relations fit which will allow me to access most information through some relatively simple joins.
My concerns are performance and Linq to SQL implication. I'm worried that Linq to SQL might start pulling an excessive amount of data and I'm worried that the practicality of such a design might hurt the long running of the application development process.
But I'm surprisingly interested in what it could mean for a more ubiquitous view of data and tagging. Basically a way of any data to have relations to any other data through this yet simple design decision.
If you think this is a good idea or see no particular problem with, please let me know! If you think there's problems with my idea, please motivate your critic but do tell me what I should look out for, or if you know of any better approach to my idea of being able to look at the data through some more common mechanism (which applies to all tables and the entire database mostly from a programming perspective).
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Sep 4, 2004
I want to make sure that usernames and folder names (that are stored in the database) are all unique when created by the admin through an admin control panel.
How would I code and use an Index to make sure that the 2 columns are unique?
I've looked at examples on the net but nothing is telling me how I can create an index through Enterprise Manager? Thanks
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Sep 4, 2004
I want to make sure that usernames and folder names (that are stored in the database) are all unique when created by the admin through an admin control panel.
How would I code and use an Index to make sure that the 2 columns are unique?
I've looked at examples on the net but nothing is telling me how I can create an index through Enterprise Manager? Thanks :)
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Jan 23, 2008
Is there a system table column to query to determine whether an index is defined as unique in SQL Server 2000? It is easy to find this info in SQL Server 2005, but I don't see a valid column for this on dbo.sysindexes.
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May 31, 2008
All- I have what i'm sure is a question with a simple answer: Supposing I want to modify the select command below to force the display of records with only unique combinations of the two fields person_id and act_session_id (bolded). How would I do this. Note that neither is a key field. (Key field headcount_id was added for completeness.)
Thanks!
SELECT hd.headcount_id, hd.person_id, hd.act_session_idFROM headcount as hd
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Nov 30, 2005
I am reading "SQL Server Query Performance Tuning Distilled",on page 104 it talks about one of the index design recommendationswhich is to choose the column that has very high selectivity of valuesinstead of a column that has very few selectivity of values.My question is if I have currently indexes on my tables that have1, 2, 3, 4, ... values only on thousands of rows, are these nonclusteredindexes pretty much useless indexes that I should get rid of?And I know that pretty much the number of selectivity values willalways remain very low.Thank you
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May 13, 2008
Hi, all.
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.
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May 13, 2008
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?
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May 29, 2001
Hi,
I am trying to figure out how to do this.
For each row, only one out of two columns(id1,id2) should be populated. So if the id1 column is already populated and the application tries to fill in something for id2 then we just simply don't want to allow that and vice versa.
I am thinking triggers is the way to go. What do you think?
thanks
Rozina
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Sep 21, 2000
using alter table syntax how can i insert the field TramingChoiceCd
Extend the constraint on NetwkChannel table UQ__TetwkChannel__50FB042B to include TramingChoiceCd
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Nov 30, 2001
Which is the preferred method Rule, Check Constraint or Trigger?
I want to set a column to todays date when the column is = "T"
else when "F" set it to a future date. Each time there is a insertion into
the table.
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Jun 7, 2004
I have a varchar field in a table.I want to restrict the entries in that field as "yes" or "no" nothing else.No record will be allowed for this field without yes or no.My question is is it possible without using any trigger for the table?I want to do it with the help of a constraint.
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Oct 13, 2004
When I see desing table option in enterprise manager of a table I don't see any constraints, but when I extract ddl I can see all 6 of them. They are all unique constraints not the check constraints. Is this normal. I am new to SQL Server and would appreciate some explanation.
Thanks
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Nov 15, 2007
Hi, i want to put a contraint on a table which much check agains two values in the same column for the same member.
For example, i don't want a male to get information based on breast cancer, and i don't want a female to get information based on prostate cancer.
I have included some sample data. Just copy and paste.
Code Block
DECLARE @MemberLookupValues TABLE (OptionID INT, ValueID INT, Description VARCHAR(20))
INSERT @MemberLookupValues VALUES (3, 10, 'Male')
INSERT @MemberLookupValues VALUES (3, 11, 'Female')
INSERT @MemberLookupValues VALUES (7, 69, 'Prostate Cancer')
INSERT @MemberLookupValues VALUES (7, 70, 'Breast Cancer')
DECLARE @MemberValues TABLE (MemberID INT, OptionID INT, ValueID INT)
INSERT @MemberValues VALUES (1, 3, 10)
INSERT @MemberValues VALUES (1, 7, 69)
INSERT @MemberValues VALUES (1, 7, 70)
INSERT @MemberValues VALUES (2, 3, 11)
INSERT @MemberValues VALUES (2, 7, 69)
SELECT * FROM @MemberLookupValues
SELECT * FROM @MemberValues
I've highlighted the values that must be stopped.
So the basic check would be, IF OptionID = 3 AND ValueID = 10 then it must not allow you to insert the values OptionID = 7 AND ValueID = 70
I hope that makes sense.
Any help will be greatly appreciated, if you need any more informaiton then just ask,
Kind Regards
Carel Greaves
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Mar 28, 2007
Hi I was wodering how to add an OR statment right in the Check Constraint expression.
This is what I am starting with in the database
([zip] like '[0-9][0-9][0-9][0-9][0-9]')
and what I want well not exact but this would answer my question
([zip] like '[0-9][0-9][0-9][0-9][0-9] || [A-Z][A-Z][A-Z][A-Z][A-Z]')
Thanks for any help
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Oct 18, 2007
Is it possible to set an index of no duplicates on a column other than the primary key of a table? If yes, how is this done?
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Jan 3, 2005
how can i implement delete constraint? i mean i don't want the rows of the primary key table to be deleted if they are used as foreign key in some other table. so i want to check if that PK is used as foreign key in other tables before deleting.
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May 13, 2006
Hi,I want to add unique contraint to EXISTING column in EXISTING table.I have ms sql 2005.How to do that?
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Oct 31, 2000
hi, I want to implement a constraint on a talbe for two fields
phone numbers should b (###)###-####
and ss# should be ###-##-####
How can I create such constraint. I tried, but got an error message and could not save the table with the new changes.
Thanks
Ahmed
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Aug 11, 1999
student --- enrollment is 1- to - many . ssn is pk in student. ssn and courseid is pk in enrollment. later I added the foreign key constraint FK_SSN in enrollment table reference student table. it is ok.
enrollment --- lessonhistory is 1-to -many, ssn, courseid and lessonid is pk in lessonhistory . I tried to set FK_SSN foreign key constraint in lessonhistory table reference enrollment table, it always show error message " no primary key in referewnce talbe enrollment "
I don't know how to fix it. could you help me out, thanks!!
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Dec 7, 2003
Can somebody tell me about on delete constraint and where should it be used - table having foriegn key?
coz want i want is- the moment i delete the data from the table whose primary key is been referenced as foreign key , The Data in all the tables where its primary key is beeen used as forein key should be deleted.
:confused:
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Nov 19, 2001
Does anyone have any Idea on how I could enforce a unique constrait across multiple tables?
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Mar 28, 2007
My company does medical billing for several clients. Each client may have a contract with several insurance companies (Payors) for rates for different procedures. I have a table named FeeSchedule with four (relevant) columns: Client, CPTCode (procedure code), Payor, and Fee.
Some Payors don't really negotiate, and have the same FeeSchedule for all clients. I know the right way to track that is have a separate set of records for each client, even for payors like medicare where every client will have the same set of records. However, the data-entry burden for populating that table would be very large, and I would like to use be able to have use a NULL client like a wildcard.
The problem is I then can't use client as part of the key, and I need to be able to restrict it so that if I have a NULL client for a specific CPT and Payor and I can't also have a another Client for that CPT and Payor.
Any ideas how to accomplish this or the equivalent functionality?
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Oct 27, 2004
Hi everybody
we have the following tables
1)
Country
Countryid CountyNAme
INIndia
MYMalaysia
UKUnitedKingdom
here Countryid is the primary key.
2) MainDept
DeptID Deptname Countryid
CMCashManagementIN
CBConsumerBankingMY
CSCustomer SupportIN
IBInternetBankIN
here deptid is the primary key
3) UserMaster
Uid Uname Deptid Countryid
001 Chris CMIN
002 Raja CSIN
003 Ram CBMY
here Uid is the primary key.
The problem is when i change the countryid from one country to another for a deptname.
THe change is not reflected in the usermaster table as it still shows the previous countryid.
For eg. user Chris belongs to dept Cash management which is situated in india.
Now if i change in mainDept table the cash management from india(IN) to say malaysia(MY).the corresponding change is not reflected in usermaster table.it still shows india. So when i query for chris in usermaster i get an error
as i am searching in india for cash mangement.
i tried using on update cascade but here it did not work as i have to make DeptID & countryID in MainDept table as composite key & use Deptid & countryid in usermaster as refernce key.
Since i have 20-25 tables also referencing the above 2 tables i have to set reference key in all these tables & these tables are in turn referenced elsewhere in other tables. Thus i end up creating a large no. of composite keys.
IS there any other way to solve this problem?
note : In sqlserver we can give on update cascade still it has the above problem
but in Oracle on update cascade is not possible
Can anybody suggest a solution for this in both sql server and in oracle
Thanks u verymuch
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Nov 30, 2005
I am having problem to find the right syntax to DROP a column with contrainst and recrate it
I get an error
if exists ( select * from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME='myTable'
and COLUMN_NAME='myDate' )
ALTER TABLE [dbo].[myTable] DROP COLUMN myDate
GO
ALTER TABLE [dbo].[myTable] WITH NOCHECK ADD
myDate datetime CONSTRAINT [DF_myDate] DEFAULT (GetDate())
GO
Query Analyser says :
Server: Msg 5074, Level 16, State 1, Line 5
The object 'DF_myDate' is dependent on column 'myDate'.
Server: Msg 4922, Level 16, State 1, Line 5
ALTER TABLE DROP COLUMN myDate failed because one or more objects access this column.
Server: Msg 2705, Level 16, State 4, Line 2
Column names in each table must be unique. Column name 'myDate' in table 'dbo.myTable' is specified more than once.
thank you for helping
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Mar 23, 2006
Hi all:
Just joined forums, so a big hello to you all :)
Just wondering if someone could explain the following two terms too me?
*Semantic Constraint
*Access Control
Are there limitations each can impose within a relational database?
Many thanks
Olly :D
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