Adding Unique constraint on the column

Use a MySQL client or command-line tool to connect to your MySQL server. You will need appropriate privileges to modify the table structure.

mysql -u <USERNAME> -p

Choose the database where your table is located.

USE <DB_NAME>;

Identify the table and column for which you want to add a unique constraint.

Use the ALTER TABLE statement to add a unique constraint to the specified column.

alter table <TABEL_NAME> add constraint <CONSTRAINT_NAME> unique (<COLUMN_NAME>);