DBMS - Mapping constraints(mapping constraints in dbms)
In a database management system (DBMS), a mapping constraint is a rule that specifies how data in one database table is related to data in another table. These constraints ensure that data is stored and organized in a consistent and logical manner within the database.
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ER model mapping constraints in dbms/mapping constraints in ER diagram
There are several types of mapping constraints that can be used in a DBMS:
1) One-to-one mapping constraint:
This constraint specifies that each row in one table can be related to only one row in another table.
2) One-to-many mapping constraint:
This constraint specifies that each row in one table can be related to multiple rows in another table.
3) Many-to-one mapping constraint:
This constraint specifies that multiple rows in one table can be related to a single row in another table.
4) Many-to-many mapping constraint:
This constraint specifies that multiple rows in one table can be related to multiple rows in another table.
Mapping constraints are often defined using foreign keys. A foreign key is a column (or set of columns) in one table that refers to a primary key in another table.
The primary key is a column (or set of columns) that uniquely identifies each row in a table. By using foreign keys and primary keys, it is possible to establish relationships between different tables in a database and enforce mapping constraints.
For example, consider a database that stores information about students and courses. There might be two tables: one for students and one for courses. The student table might include columns for student ID, name, and major, while the course table might include columns for course ID, name, and instructor. To establish a many-to-many relationship between students and courses (i.e., a student can take multiple courses and a course can have multiple students), a third table called "enrollments" could be created. This table would have foreign keys for student ID and course ID, as well as additional columns for the enrollment date and any other relevant information. By using foreign keys to link the enrollments table to the student and course tables, a many-to-many mapping constraint could be established.
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Created by-- HARSH CHAUHAN
