Sql Query To Use a Unique Key

Unique Key Constraint is used, when we want to keep the value of a specific column unique i.e non-repeatable. After creating a table using a unique key constraint, it doesn’t allow to insert of repeated value.

It will give an error (UNIQUE constraint failed: user_detail.email) while inserting the same email "[email protected]" more than one time.

SQL Query
create table user_detail ( id int primary key, email varchar(50) unique ); INSERT INTO user_detail VALUES(1,"[email protected]"); SELECT * FROM user_detail; INSERT INTO user_detail VALUES(2,"[email protected]");