Course Content

  • Notes for SQL Constraints

Course Content


SQL constraints are rules that a table's data must follow. The type of data that can be entered into a table is limited by constraints. This ensures that the data in the table is accurate and reliable. The action is cancelled if there is a conflict between the constraint and the data action.

  • Domain constraint.
  • Tuple Uniqueness constraint.
  • Key constraint.
  • Entity Integrity constraint.
  • Referential Integrity constraint.

There are six basic limitations that are often used in SQL Server, and we'll go through them in depth with examples in this and the following articles.

There are five different types of constraints: A NOT NULL constraint is a restriction in a table that forbids null values from being entered in one or more columns. A unique constraint (also known as a unique key constraint) is a rule in a table that prevents duplicate values in one or more columns.

  • Problem: You want to find the names of the constraints in a table in SQL Server.
  • Example: We want to display the names of the constraints in the table student.
  • Discussion: Use the view table_constraints in the information_schema schema.

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