Unique Constraint On Multiple Columns

Oct 31, 2005

Can you create a unique constraint on multiple columns, or does it have
to be implemented as a unique index?

If possible can someone please post some sample code?

Thanks,

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Unique Constraint W Nulls, Compare Columns

Jun 20, 2008

Hi Guys.

I have a problem. I have two feilds in a table. Both of them are (int). I want to be able make sure the same number is not put in both columns for each row. Both colums have to be a different number, and also if one is null, the other cannot be. How do I go about enforcing this policy?

For Example:

This is what I want

ID Column1 Column2
--- -------- ---------
1 5 8
2 5 7
3 null 10
4 6 2


This is what I DO NOT want:

ID Column1 Column2
--- -------- ---------
1 5 5
2 5 5
3 7 7
4 null null


I created a unique constraint between the 2 columns, but it still allows dups within the row. Please help me.

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How To Create A Unique Constraint On Composite Columns

May 5, 2008

I am trying to create a Unique Constraint on a SQL Server 2005 table where the uniqueness is based on 2 columns.

Could anybody provided some help on how I could enforce this on an existing table (link, or example) I have been looking around without luck.

Thanks in advance

John.

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SQL Server 2014 :: Find Views Which Has More Than 16 Columns For Unique Index / Constraint

Oct 27, 2015

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...

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Unique Constraint Doesn't Allow Multiple Null Values In Server?

Jun 2, 2014

Why we the Unique Constraint doesn't allow the multiple null values in Sql Server?

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Multiple Columns Constraint

Oct 28, 2003

I need to setup a constraint to 2 columns(combine keys). Is there a way to accomplish this without using trigger?

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T-SQL (SS2K8) :: Check Constraint On Multiple Columns

Jul 25, 2014

I have a case where if the Id field is a specific value, I don't want to allow null in another field, but if the Id value <> a specific value, null is ok.

In the example below, inserting the first record should succeed, the second should succeed, and the 3rd should fail. Right now the 2nd two fail. I gotta be missing something easy, but I can't figure it out.

USE tempdb
GO
IF OBJECT_ID('tempdb.dbo.CheckConstraintTest') IS NOT NULL
DROP TABLE tempdb.dbo.CheckConstraintTest;
CREATE TABLE CheckConstraintTest

[Code] .....

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Create Unique Index On Multiple Columns

Jan 19, 2008

Hello, I will explain myself further. I want to make my table in such a way that no two colums have the same value for example:
Row 1 - Column 1 = "cool"
Row 1 - Column 3 = 91
Row 3 - Column 1 = "cool"
Row 3 - Column 3 = 91
 
I dont care about one column having duplicate values, I want to protect against  Column 1 and 3 having the same values on other rows. Is this possible to do in sql server?

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What Is The Difference Between A UNIQUE INDEX And A UNIQUE CONSTRAINT?

Sep 22, 2004

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.

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Unique Constraint Vs Unique Index In MS SQL 2000

Jul 20, 2005

HelloWhat should I use for better perfomance sinceunique constraint always use index ?ThanksKamil

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Unique Constraint And Unique Index, What's The Difference?

Jun 24, 2006

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?

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Unique Constraint Error When There Is No Constraint

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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Unique Index Vs Unique Constraint

Mar 7, 2001

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 ?

Which one do one use ?

thanks
sonali

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Unique Constraint Vs Unique Index

Jan 20, 2006

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?

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Add UNIQUE Constraint

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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Unique Constraint

Nov 19, 2001

Does anyone have any Idea on how I could enforce a unique constrait across multiple tables?

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Unique Constraint

May 19, 2004

What is the simplest way to add a unique constraint on a field of type varchar(7) that can allow any number of <NULL>'s?

I only want to ensure that when this field is updated, it is updated with a value that has not been used.


IF EXISTS (SELECT Project FROM tbProjects WHERE Project = @cProject)
RAISERROR('Project number already used!',16,1)
ELSE
UPDATE tbProjects SET Project = @cProject WHERE ProjectID = @iProjectID
GO


Also, I cannot allow the user to chante the project field value once it is set.


Any suggestions?

Mike B

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Unique Constraint

Apr 4, 2008

Anybody knows how to make two columns in a table unique?

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UNIQUE Constraint

Aug 16, 2006

i'm just creating a table, no data as yet.

i have a varchar(15) fld with Nulls NOT allowed

i want to create a constraint that this field named ipkey be UNIQUE.

I'm having trouble with the syntax for the constraint expression.

i've typed in the SQL Server Managment Studio Express Expression field:
UNIQUE(ipkey)
and
@unq_ipkey UNIQUE(ipkey)

SQL Server Managment Studio Express complains:
"Error validating constrating, do you want to edit expression"

So - what am i doing wrong?
And thanks for taking the time to help.

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Unique Constraint

Dec 3, 2007

Hi,

I have a table with two column, c1 and c2. c1 is set as primary key. I want c2 to be set with unique constraint.

I choose this talbe in object explorer, right click and select modify. Then I choose "index/key" from "table designer" menu.

The problem is that in the "index/key" dialog, the "Columns" item (under General) is always c1. if I click the "..." button to popup "index column", I could only choose either "c1" or <None> under "column name" dropdownlist.

How could I choose c2 and set unique constraint on it?

Thx
Tao

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Constraint Unique Row

Apr 11, 2008



Hi,

I need to define a constraint , to prevent some fields of a table to be duplicated, How can i define this constraint ?

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A Unique Unique Constraint

May 1, 2008

Here is the table I created:

create table Test (
[recId] [int] identity(1, 1) not null,
[code] [varchar](50) not null,
[prime] [bit] not null constraint [DF_Test_prime] default (cast(0 as bit)),
constraint [PK_Test] primary key clustered
(
[recId]
) with fillfactor = 90 on [primary]
) on [primary]
go

insert into Test (code, prime) values ('AVA', cast(1 as bit))
insert into Test (code, prime) values ('BUS', cast(1 as bit))
insert into Test (code, prime) values ('BUS', cast(0 as bit))
insert into Test (code, prime) values ('BUS', cast(0 as bit))
insert into Test (code, prime) values ('CAR', cast(1 as bit))
insert into Test (code, prime) values ('CAR', cast(0 as bit))
insert into Test (code, prime) values ('RLW', cast(1 as bit))
insert into Test (code, prime) values ('RLW', cast(0 as bit))
insert into Test (code, prime) values ('RLW', cast(0 as bit))

select *
from Test

I need to create a constraint on this table that will not allow me to have two rows that are prime for the same code. So the following insert statement should fail:

-- This should fail
insert into Test (code, prime) values ('RLW', cast(1 as bit))


Thanks for you help!

Regards,
Anand

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Sql Exception Unique Key Constraint

Oct 25, 2007

 
Hi All,
I am trying to catch a specfic unique key constraint in a table.
i my table i have two fields USERID And EMAILID and i set both to unique.
now on registration form i am checking that USERID or EMAIID is already present or not.
by taking ex.number =2627 i am not able to find which unique key constraint is getting violated.
is there any other way to find it.
thanks in advance.

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Can&#39;t Create Unique Constraint

Nov 3, 2000

I am attempting to create a unique constraint on an nvarchar field named theology (it is not the primary key field)
that allows nulls. The table contains multiple rows with the value of null for
field theology. The documentation says one can create a unique constraint on a
field with all unique value except for null. Here is the error message:

'testtable1' table
- Unable to create index 'IX_testtable1'.
ODBC error: [Microsoft][ODBC SQL Server Driver][SQL Server]CREATE UNIQUE INDEX
terminated because a duplicate key was found. Most significant primary key
is ''.
[Microsoft][ODBC SQL Server Driver][SQL Server]Could not create constraint. See
previous errors.

Any ideas? I am creating a unique constraint and not a unique index. Is there
some other database option to set to allow this?

.

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Unique Constraint Question

Sep 12, 2003

when we use Unique constraint over a column it allows null values.
but then null values are duplicating, how is that?

thanks

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Unique Constraint With Conditioning?

May 4, 2005

Hi All:

Is there a way to create a unique constraint with 4 fields combined, such as colA, colB, colC, and colD.

but colD is for all the values but value = 3.

If this does not work out, trigger probably is the last way I would like to approach. and it is slower than constraint with many inserts.

thanks
David

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Add Unique Constraint On 3 Fields?

Jul 21, 2015

I want to add a unique constraint on 3 fields, to only allow the value in the field ONE time. The value will NEVER be the same for anything else. This is the table structure

Code:
Create Table Employees
(
P_Id int NOT NULL,
InstructorName varchar(255) NOT NULL,
CourseName varchar(100) NOT NULL,
DataTableName varchar(100) NOT NULL
)

I want to create a unique constraint across the fields Instructorname, CourseName, DataTableName as their is ONLY 1 instructor per course per table so those 3 fields will ALWAYS hold unique values. I think the constraint syntax would go like so, but want to check before I go butchering some sql syntax.

constraint syntax:

Code:
Alter Table Employees
Contstraint uniqueEmployee Unique (InstructorName ,CourseName ,DataTableName )

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Unique Constraint/index

Feb 12, 2004

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

Thanks in advance

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Unique Constraint/Index

May 7, 2008

What is the difference between unqiue constraint and unique index? What are the pros and cons? Are they interchangable?

------------------------
I think, therefore I am - Rene Descartes

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Add Unique Constraint Problem.

May 16, 2008

hi
i create a sample table by this code and insert some values to it :

create table test(
c1 int,
c2 int)

insert test select 1,2
insert test select 2,44
insert test select 3,56

now, i want to add new column with unique constraint by this code :

alter table test
add c3 int unique

but the following error has shown me :

Msg 1505, Level 16, State 1, Line 1
CREATE UNIQUE INDEX terminated because a duplicate key was found for object name 'dbo.test' and index name 'UQ__test__2D27B809'. The duplicate key value is (<NULL>).
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
The statement has been terminated.

where does my problem and how to solve it ?
thaniks

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How Can We Have UNIQUE Constraint To The Table...

May 19, 2008

Hello...
I was confused with UNIQUE key. Its easy to create PRIMARY KEY to the Table. Now how to alter the Table to have UNIQUE key...

Thanks
Ganesh

Solutions are easy. Understanding the problem, now, that's the hard part

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Unique Column Constraint

Jun 6, 2008

I like to use the management console to design tables, but have
been unable to figure out how to add a unique column constraint.

I have a primary key defined in col1 and want to make col2, char(10),
unique, but keep col1 as the primary key.

I have tried the Check constraint menu path, but do not know how
to write the expression.

If I go along the Indexes/Key path, I am forced to change the primary
key which I do not want to do.

Can anyone help?

TIA, Joe

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Unique / Check Constraint?

Jun 19, 2008

I have a table called tblImages with the following columns:

ImageID [int]
UserID [int]
MainImg [bit]

what i need to ensure is that only one MainImage can be = 1 (true) for each userId at any one time.

any idea what i need to do?

alex

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