Primary key is the unique attribute among all attributes of an object, which alone is sufficient to represent a sigle entity.
for example
a table has columns student id, stdent name, father name, class, department etc.
so here "student id" is primary key bcoz it cann't be same for two students, where other attributes like name and class can be same for more than one student.
hence primary key is the attribute which represent a unique entity and is sufficient to search the tuple (row) of table having that primary key value.
Firdous Anjum The Great :)
COMSATS Institute of Information Technology, Lahore.
No, all tables do not have primary key. Primary must be explicitly defined and must not be null.
The Primary Key
primary keys are unique
it key that will enable you link the two tables together for relationship
It is a field in one table that is a primary key in another table. It is used to create a relationship between two tables, normally a one to many relationship. The one side is where it is the primary key and where it is the foreign key, that is the many tables.
Foreign key is used to define a relationship between two tables by referencing the primary key of another table. It ensures data integrity and enforces referential integrity between the related tables.
It is the DBMS that ensures the value of the foreign key matches another table's primary key when referential integrity constraints are enabled within the DBMS
True.
Primary key
A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.
A non-key field can be any field in the table that is not the primary key. During the process of normalisation identifying non-key fields is important, as they and other fields may be moved and new tables created. Foreign keys will be left in the table.
establishing a relation between two tables called fornkey.......the colum name should be unique is called "primary key"...a table contain only one primary key...a table contain more then one fornkey....