Different types of constraints and difference between primary key and foreign key?

Question

Accepted Answer

Explanation of different types of constraints and primary key vs foreign key

Constraints are rules applied to columns to maintain data integrity
Types of constraints include NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK, and DEFAULT
Primary key is a unique identifier for a row in a table, while foreign key is a reference to a primary key in another table
Primary key cannot have null values, while foreign key can have null values
Primary key is used to enforce entity integrity, while foreign key is used to enforce referential integrity

Accepted Answer

Constraints - Not null, primary key, unique, foreign key, informational, table etc. constraints. A primary key generally focuses on the uniqueness of the table. It assures the value in the specific column is unique. A foreign key is generally used to build a relationship between the two tables. The table allows only one primary key.

Different types of constraints and difference between primary key and foreign key?

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