Constraints in Sql server

C# Corner

Jaya Prakash

3y1.1kSQL Server

my table

create table coursedept (did (pk,fk,varchar(50),notnull,

(cid (pk,fk,varchar(50),notnull) )

how to add pk and fk for same column

ive already created did(department table ) and cid(course table) with primary key i need to combined these two table

coursedept(did ,cid)

pls help me how to do it

4 Replies

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Sachin Singh3y ago
Accepted answer
see,

there can be unlimited number of foreign keys in a table, so did and cid can easily be marked as foreign key.

second, yes we can have two primary keys we call them composite key.

Your bridge table should look like this
```
 create table CourseDept
{
DId INT NOT NULL,
CId INT NOT NULL,
PRIMARY KEY (DId,CId),
FOREIGN KEY (DId) REFERENCES Department(DId)
FOREIGN KEY (CId) REFERENCES Course(CId)
}
```

Rajeev Kumar3y ago

CREATE TABLE coursedept (
  DId NVARCHAR(10) NOT NULL, CId NVARCHAR(10) NOT NULL, 
PRIMARY KEY (DId,CId), 
FOREIGN KEY (DId) REFERENCES Department(DId), 
FOREIGN KEY (CId) REFERENCES Course(CId))

Mahesh Chand3y ago
Here is the detailed tutorial on this topic: Constraints in SQL Server (c-sharpcorner.com)

https://www.c-sharpcorner.com/UploadFile/f0b2ed/constraints-in-sql-server/

Deepak Tewatia3y ago

Hi Jaya Prakash,
you can use the following query:

ALTER TABLE coursedept
ADD PRIMARY KEY (did),  -- add primary key
ADD FOREIGN KEY (cid) REFERENCES course(cid);  -- add foreign key