DBMS Integrity Constraints

Integrity constraints are the set of predefined rules that are used to maintain the quality of information. Integrity constraints ensure that the data insertion, data updating, data deleting and other processes have to be performed in such a way that the data integrity is not affected. They act as guidelines ensuring that data in the database remain accurate and consistent. So, integrity constraints are used to protect databases. The various types of integrity constraints are

Types of Integrity Constraints

There are four types of integrity constraints which are:

• Domain Constraints
• Entity integrity Constraints
• Key Constraints
• Referential integrity constraints

Domain Constraints

These are defined as the defination of valid set of values for an atribute. The data type of domain include string, char, time, integer, date, currency etc. The value of the attribute must be avialable in comparable domains.

Example:

Student_Id	Name	Semester	Age
21CSE100	Ramesh	5th	20
21CSE101	Kamlesh	5th	21
21CSE102	Aakash	5th	22
21CSE103	Mukesh	5th	20

Entity Integrity Constraints

Entity integrity constraints state that primary key can never contain null value because primary key is used to determine individual rows in a relation uniquely, if primary key contains null value then we cannot identify those rows. A table can contain null value in it except primary key field.

Example:

It is not allowed because it is containing primary key as NULL value.

Student_id	Name	Semester	Age
21CSE101	Ramesh	5th	20
21CSE102	Kamlesh	5th	21
21CSE103	Aakash	5th	22
	Mukesh	5th	20

Key Constraints

Keys are the entity set that are used to identify an entity within its entity set uniquely. An entity set can contain multiple keys, bit out of them one key will be primary key. A primary key is always unique, it does not contain any null value in table.

Example:

Student_id	Name	Semester	Age
21CSE101	Ramesh	5th	20
21CSE102	Kamlesh	5th	21
21CSE103	Aakash	5th	22
21CSE102	Mukesh	5th	20

It is now acceptable because all rows must be unique.

Referential integrity constraints

It can be specified between two tables. In case of referential integrity constraints, if a Foreign key in Table 1 refers to Primary key of Table 2 then every value of the Foreign key in Table 1 must be null or avialable in Table 2.

Example:

Here, in below example Block_No 22 entry is not allowed because it is not present in 2nd table.

Student_id	Name	Semester	Block_No
22CSE101	Ramesh	5th	20
21CSE105	Kamlesh	6th	21
22CSE102	Aakash	5th	20
23CSE106	Mukesh	2nd	22

Block_No	Block Location
20	Chandigarh
21	Punjab
25	Delhi

Conclusion

Integrity constraints act as the backbone of reliable and robust database. They ensure that the data stored is reliable, worthy, consistent and accurate within the database. By implement integrity constraints we can improve the quality of the data stored in database. So, as the database continues to grow it will not become inconsistent and inaccurate.

Frequently Asked Questions on Integrity Constraints – FAQs

What are integrity constraints and why are they important in database?

Integrity constraints are predefined rules which ensures the quality of the information in databases. They maintain data accuracy and consistency by guiding the operations like data insertion, data deletion and data updation. These are important for protecting the integrity of the database.

What are the key types of integrity constraints and, how do they differ?

Basically there are four types of integrity constraints these are Domain constraints, Entity integrity constraints, key constraints and Referential integrity constraints. Each type of these serve their purpose in maintaining data integrity.

How do domain constraints contribute to data integrity in databases?

Domain constraints define valid sets of values for attributes, ensuring that data entered into the database adhere to specified data types and formats. By enforcing these constraints, databases maintain consistency and accuracy of data, preventing the insertion of incorrect or incompatible values.