Frequently Asked Questions on Unique Constraint
What is a unique constraint in SQL?
A UNIQUE constraint ensures that all values in a column are unique. UNIQUE and PRIMARY KEY constraints provide uniqueness guarantees for a column or set of columns. PRIMARY KEY constraints automatically have UNIQUE constraints.
SQL | UNIQUE Constraint
SQL Constraints Unique constraints in SQL is used to check whether the sub-query has duplicate tuples in its result. It returns a boolean value indicating the presence/absence of duplicate tuples. Unique constraint returns true only if the subquery has no duplicate tuples, else it returns false.