Monthly Payment Calculator Backend

DB Table (MariaDB)

create table user ( id bigint auto_increment primary key, username varchar(50) not null, password varchar(255) not null, role varchar(20) default 'USER' not null, created_at timestamp default current_timestamp() not null, constraint username unique (username) );

create table payment ( id bigint auto_increment primary key, product_name varchar(255) not null, total_price decimal(10, 2) null, monthly_rate decimal(10, 2) not null, remaining_months int not null, is_rate_adjustable tinyint(1) default 0 null, loan_type enum ('ZERO_INTEREST', 'PERSONAL', 'MORTGAGE') not null, user_id bigint not null, created_at timestamp default current_timestamp() not null, constraint unique_product_name unique (product_name), constraint payments_FK foreign key (user_id) references user (id) );