Integrity constraints in dbms|SKILLS ARENA

Integrity constraints in dbms

Integrity constraints are rules that are used to ensure the accuracy and consistency of data in a database. They are used to specify the data that is allowed in a database and the relationships between different data elements.

Integrity constraints in dbms SKILLS ARENA

There are several types of integrity constraints that can be used in a database:

NOT NULL constraint:

This constraint specifies that a column cannot contain a NULL value. For example, if we have a table with a column age that has a NOT NULL constraint, we cannot insert a NULL value into that column.

UNIQUE constraint:

This constraint ensures that all the values in a column are unique. For example, if we have a table with a column email that has a UNIQUE constraint, we cannot insert two rows with the same email address.

PRIMARY KEY constraint:

This constraint defines a column or set of columns as the primary key of a table. The primary key is used to uniquely identify each row in the table and it cannot contain NULL values.

FOREIGN KEY constraint:

This constraint is used to enforce referential integrity in a database. It specifies that the values in a column (or set of columns) must match the values in the primary key of another table. For example, if we have a table called orders with a column customer_id that is a foreign key to the customers table, we cannot insert an order for a customer that does not exist in the customers table.

CHECK constraint:

This constraint is used to specify a condition that must be met by the data in a column. For example, if we have a table with a column age that has a CHECK constraint specifying that the age must be greater than 18, we cannot insert a row with an age value of 17.

Here is an example of how you might use these constraints in a SQL table:


CREATE TABLE customers (
    customer_id INT PRIMARY KEY,
    first_name VARCHAR(255) NOT NULL,
    last_name VARCHAR(255) NOT NULL,
    email VARCHAR(255) UNIQUE NOT NULL,
    age INT CHECK (age > 18)
); 
CREATE TABLE orders (
    order_id INT PRIMARY KEY,
    customer_id INT FOREIGN KEY REFERENCES customers(customer_id),
    order_total DECIMAL NOT NULL
);

In this example, we have created two tables: customers and orders. The customers table has a primary key column customer_id and three other columns with NOT NULL constraints. The email column also has a UNIQUE constraint and the age column has a CHECK constraint. The orders table has a primary key column order_id and a foreign key column customer_id that references the customer_id column in the customers table. The order_total column has a NOT NULL constraint.

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Created by-- HARSH CHAUHAN

Integrity constraints in dbms|SKILLS ARENA