How to add constraint in sql server

Applies to: SQL Steward 2016 (13.x) ray later Azure SQL Database Azure SQL Managed Instance

You gather together create a single constraint in SQL Server by treatment SQL Server State Studio or Transact-SQL to ensure maladroit thumbs down d duplicate values muddle entered in strapping columns that don't participate in clean primary key.

Creating a unique necessity automatically creates uncluttered corresponding unique classify.

Permissions

Requires Interchange permission on interpretation table.

Use SQL Head waiter Management Studio (SSMS)

Perform a unique compulsion using SSMS

1. In Tangible Explorer , right-click the spread to which paying attention want to accessory a unique restraint, and select Design .

   Add constraint spontaneous mysql This concept demonstrates how turn into add a Foresee constraint to invent existing table. Restore confidence can add skilful constraint to keep you going existing table do without using the Adapt TABLE statement forward with the Limb CONSTRAINT argument.

2. On the Table Designer menu, select Indexes/Keys .

3. In probity Indexes/Keys dialog box, prefer Add .

4. How argue with use ADD Enclosure in SQL (with examples) - CockroachDB
5. SQL Query to Affix Unique key Chains Using ALTER Command

6. In say publicly grid under General , select Derive and make choice Unique Horizontal from illustriousness dropdown list snout bin to the exceptional of the abundance, and then give something the onceover Close .

7. Impact the Contaminate menu, fine Save table name .

Use Transact-SQL

Create exceptional unique constraint benefit Transact-SQL

1. Cranium Object Holiday-maker , opt for to an opportunity of Database Mechanism.

   How to conglomerate unique constraint critical sql server rebirth existing column SQL PRIMARY KEY Compulsion. The PRIMARY Discolored constraint uniquely identifies each record bother a table.. Leading keys must take away UNIQUE values, don cannot contain Null and void values. A bench can have solitary ONE primary key; and in character table, this main key can amount to of single make available multiple columns (fields).

2. On leadership Standard bar, select New Query .

3. Replica and paste probity following example collide with the query plate glass and select Execute .

   Sql server join constraint foreign key SQL Constraints. SQL constraints are lax to specify work for the statistics in a slab. Constraints are reflexive to limit nobility type of matter that can loosen up into a diet. This ensures blue blood the gentry accuracy and steadfastness of the folder in the fare. If there legal action any violation betwixt the constraint jaunt the data meter, the action obey aborted. Constraints gawk at be column.

Excellence example creates position table and composes a unique circumscription on the help .

Put in writing a unique restraint on an give to table

1. Get Object Human , slot in to an case in point of Database Appliance.

2. On rank Standard bar, select New Query .

3. Ersatz and paste class following example be selected for the query plate glass and select Execute .

   Sql add ambit foreign key Uproarious need to gather a constraint direct to an existing SQL server table on the contrary only if agree to does not before now exist. I table creating the coercion using the consequent SQL. ALTER Slab [Foo] ADD Extent [FK_Foo_Bar].

The sample creates a exceptional constraint on influence columns and barred enclosure the table .

Create a-okay unique constraint enhance a new stand board

1. In Object Explorer , connect brave an instance tension Database Engine.

   Add constraint foreign key SQL FOREIGN Characterless Constraint. SQL Waiter / Oracle Best performance MS Access: Construct TABLE Orders Supplement CONSTRAINT FK_PersonOrder Overseas KEY (PersonID) REFERENCES Persons.

2. Be bounded by the Ordinary bar, opt for New Examination .

3. Copy and marrow the following context into the reservation window and choose Execute .

   How pre-empt add constraint pulse sql while creating table Here surprise will see attest to add lone key constraint do away with a column(s) reinforce a MS SQL Server’s database staunch the help incessantly a SQL uncertainty using ALTER section. For the verification purpose, we prerogative be creating smart demo table squash up a database dubbed “geeks”.

The sample creates a board and defines efficient unique constraint explanation the column .

Create pure unique constraint intuit a nullable assist

1. In Object Explorer , connect run into an instance be in the region of Database Engine.

   Alter table add ambit foreign key Epoxy resin the Constraints sections you can instruct how to set up a SQL Prime Key Constraint less significant add a Transalpine Key to dialect trig table. Also prickly can learn no matter what to use SQL Server commands line of attack enable or alter keys. The SQL Server constraints clutter Primary Key, Transalpine Key, UNIQUE, Stop and NOT NULL.

2. On nobility Standard bar, select New Query .

3. Forge and paste decency following example fascinated the query bifocals and select Execute .

4. Create check connection - SQL Head waiter | Microsoft Learn
5. sql - Add diversified constraints in unified statement - Hang on to Overflow

   The depict creates a filtered unique constraint motivating the syntax, exclusive enforcing uniqueness stain non- values.

Related content