All about Unique Constraints

Let us understand all the details with respect to Unique Contraints.

  • There can be more than one Unique Contraint in a given table.
  • Unique Constraint enforces uniqueness but values in the Unique Constraint Columns can be empty.
  • Unique Constraint contain one or more columns in a table. If there are more than one column then it is called as composite key .
  • Unique Constraint columns can be surrogate where the values might be populated using sequence. However, it is not very common and not a good practice.
  • We can define Foreign Key Constraints in Child Tables using Primary Key or Unique Constraints in the table.
  • An index will be created when we define Unique Constraint to sort the data and enforce uniqueness.

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