security-admin/db/mysql/patches/023-add-unique-constraint-on-table-x_user.sql

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drop procedure if exists create_unique_constraint_on_username;

delimiter ;;
create procedure create_unique_constraint_on_username() begin
DECLARE loginID bigint(20);
 /* check tables exist or not */
	if exists (select * from information_schema.columns where table_schema=database() and table_name = 'x_user' and column_name='user_name') then
 		/* check unique constraint exist on user_name column or not */
	 	if not exists (select * from information_schema.columns where table_schema=database() and table_name = 'x_user' and column_name='user_name' and column_key='UNI') then
	 		if not exists (select * from information_schema.table_constraints where table_schema=database() and table_name = 'x_user' and constraint_name='x_user_UK_user_name') then
	 			ALTER TABLE x_user MODIFY COLUMN user_name varchar(767) NOT NULL, ADD CONSTRAINT x_user_UK_user_name UNIQUE(user_name(767)); 
	 		end if;
	 	end if;
	end if;
end;;

delimiter ;
call create_unique_constraint_on_username();

drop procedure if exists create_unique_constraint_on_username;