SQL constraints are used to specify rules for the data in a table. They ensure the accuracy and integrity of the data in the database. Common constraints include PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, CHECK, DEFAULT, and INDEX.

List of Constraints

• PRIMARY KEY: Uniquely identifies each record in a table.
• FOREIGN KEY: Links two tables.
• UNIQUE: Ensures all values in a column are different.
• NOT NULL: Ensures a column cannot have a NULL value.
• CHECK: Ensures values in a column meet a specific condition.
• DEFAULT: Sets a default value for a column if no value is specified.
• INDEX: Improves the speed of data retrieval.