Introduction to constraints in SQL Language

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What does constraints in SQL mean? Which are the different types of Integrity Constraints? What happens if a constraint is violated?

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Introduction to constraints in SQL Language



 Constraints are some rules/ restrictions specified by the user in order to enter values within a determined range or not allowing the user to enter data containing a particular type of input. There are three types of Integrity constraints:
Domain Integrity Constraint
Entity Integrity Constraint
Referential Integrity Constraint
When any of the constraints mentioned by the database developer are violated, a message appears on the screen saying that a constraint was violated with the name of the constraint that was violated so that the user gets to know what types of values he/she is allowed to enter into the database.

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