In DBMS, a relationship refers to the way in which two or more data sets are linked, or any association between two entity types. Entities take part in the relationship, and it is represented by a diamond shape. There are three main types of relationships that can exist between tables in a relational database:
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One-to-One Relationship (1:1): This type of relationship is used to create a relationship between two tables in which a single row of the first table can only be related to one and only one record of a second table. Similarly, the row of a second table can also be related to only one row of the first table.
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One-to-Many Relationship: This type of relationship is used to create a relationship between two tables in which any single row of the first table can be related to one or more rows of the second table, but the rows of the second table can only relate to the only row in the first table. It is also known as a many-to-one relationship.
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Many-to-Many Relationship: This type of relationship exists when each record of one table can be related to one or more than one record of the other table, and vice versa.
Relationships in a database are important because they help in storing data in separate tables and make it easier to manage and retrieve data.
