What are Keys in DBMS? Different Types of Keys

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There is a lot of data available in this digital world. Every computer and application works with a database system. DBMS facilitates the effective management of these systems.

For maintaining the integrity and efficiency of data, keys in DBMS play an important role. It allows smooth and effective data manipulation. An overview of keys in DBMS and its different types is given in this article.

Database management system (DBMS)

An electronically organized collection of structured data in a computer system is called a database. DBMS usually manages it. Database management system is a software system to manage databases. DBMS enables structured data creation, storage, management, and retrieval for users. Additionally, it provides database security and access control administration. It offers features like data modeling, security, privacy, integrity, consistency, storage, retrieval, sharing, backup, and recovery. DBMS is like an interface between database and software applications, end users, and programmers. Different keys in DBMS are used for this purpose.

There are four main components of DBMS: the modeling language, data structure, database query language, and transaction mechanisms.

DBMS are of two types: relational (SQL) and non-relational (NoSQL). Data is kept in tables with a set of rows and columns in relational DBMS. While non-relational DBMS stores data as key-value pairs, documents, and graph-based models. DBMS facilitates easy management of large data sets and easy and effective access to stored data.

Keys in DBMS

In database management systems, especially in relational databases, keys play a significant role. It helps for effective data retrieval while maintaining data integrity. It enables databases to organize, protect, and deliver data efficiently. Also, it ensures smooth and effective data manipulation. Keys are essential for classifying different sorts of data. 

The DBMS key is either an attribute (column) or a set of attributes that help to identify a row (record) in a table(relation). It is used to create and identify the relationships between different columns and tables in a database. By combining one or more columns in the table, the keys in DBMS enable you to identify each row in the table uniquely. Many columns and tables of a relational database can be related to one another through keys. The unique individual values present in a key are often referred to as key values. Furthermore, the key is also useful for finding specific records or rows from a table.

In practical applications, databases store massive amounts of data from multiple tables. There can be thousands of such rows. Moreover, there will be duplicate rows and errors that deliver inaccurate reports from the database. Also, even though the tables are separated, they still share some common relationships. The concept of keys is to solve all these problems. Keys in relational DBMS help to identify all these rows uniquely and separately despite these challenges. Keys act as unique identifiers and provide each record with a unique identity. It ensures that the relationships that apply to any record are accurate and unrepeated.  

Types of keys in DBMS

There are mainly 8 types of DBMS keys based on the requirements. Each type of key has unique characteristics and functions of its own. The different keys in DBMS are given below.

1. Primary Key

It is a column or a set of columns that helps to identify each row in a table uniquely. Every table must have a primary key, and each table only has one primary key. Furthermore, the primary key value cannot be null. It must always be unique without any duplicates. Two rows in a table cannot have the same primary key value. The values of the primary key can never be modified or updated. Additionally, the primary key selection is based on the requirement. It can be a single column or a set of columns.

2. Candidate key

It is a column or group of columns that uniquely identifies rows in a table. It always has unique values and must not contain null values. Every table must have one single candidate key, and there can be more than one candidate key. Among these candidate keys, the primary key is chosen. So, these keys are as strong as the primary key and have the same properties as the primary keys.      

3. Super key

It is one of the keys in DBMS which is either a single key or a group of keys that help to uniquely identify all the rows in a table. A super key is not only a combination but also a superset of candidate keys. There may be more than one super key, but it always has at least one. It may consist of any number of values and null values. Furthermore, all the attributes are sufficient for the unique identification of rows but all of them may not be necessary.

4. Foreign key

It is a column or group of columns in a table to point to the primary key of another table. Foreign keys establish relationships between two tables. It acts like a connector between the tables. It ensures data and referential integrity and consistency across tables. Most of the time foreign key is not unique, and it can take a null value. This key may have a name other than that of a primary key. Also, it combines two or more tables at a time. We can easily retrieve data from both tables using this key. 

5. Composite key

It is a set of two or more columns or attributes that uniquely identify each row in a table. This key is useful when a single column is not enough to identify a row uniquely. When considered separately, the columns in the set may not be unique. However, they ensure total uniqueness when combined.

6. Alternate key

These are candidate keys in DBMS that are not the primary key. It is a secondary key. A table can have multiple candidate keys. However, only one can be chosen as the primary key. Because a table has only one primary key. So, all the other remaining candidate keys are called alternate keys. If there is only one candidate key in a relation, it doesn’t have an alternate key.  

7. Unique key 

It is either a column or a set of columns that uniquely identifies each row in a table. This key is unique for all the rows of the table. It ensures each value in a column is distinct. These keys are similar to primary keys because both contain unique identifiers for the rows in a table. However, a unique key can have a null value, whereas a primary key cannot. It prevents duplicates, and it is non-updatable.    

8. Artificial key 

These keys are created using arbitrarily assigned data. It is an extra column added to the table to serve as a primary key. We create this type of key when the primary key is large and complex. In SQL, this key is usually an integer and numbers the artificial key values in a serial order. Furthermore, these keys are unique, updatable, and cannot be a null value.  

All these different keys in DBMS have their own functionality, uses, and characteristics. One must implement appropriately for the relevant database based on the attributes used to identify the object. The correct identification and implementation lead to accuracy in the database and improved results in a limited time. 

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Conclusion

In summary, DBMS keys play an important role in efficient database management. It helps for effective management and manipulation of data by ensuring data integrity. Users widely use these keys not only to uniquely create but also to identify the rows in the database. There are different keys in DBMS with unique functionality. These keys facilitate effective data organization, integrity, and retrieval. A solid understanding of these keys helps for seamless and effective database management. 

Recommended Reads:

• Relational Database Management System
• Database Management System and its types
• Difference between SQL and Microsoft SQL server
• What is RDBMS? | Relational Database Management System
• What is Database? What is Database Management System and its Types?

FAQ‘s

Q1. What is SQL?

Ans. Structured Query Language (SQL) is a computer language. Relational DBMS uses it to manage data.

Q2. Which DBMS does use keys?

Ans. Relational (SQL) databases use different DBMS keys.

Q3. Can multiple tables have the same primary Key?

Ans. Yes. In multiple tables, you can have the same column names as the primary key.

Q4. Is the primary key mandatory?

Ans. Yes. In order to maintain integrity, a table must always have a primary key. Additionally, a table only has one primary key.

Q5. What is a secondary key?

Ans. It is an additional or alternative key in addition to the primary key to locate specific data.

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