-- 테이블 생성 SQL - user_table
CREATE TABLE user_table
(
    `user_id`       INT            NOT NULL    AUTO_INCREMENT, 
    `user_name`     VARCHAR(20)    NOT NULL, 
    `phone_number`  VARCHAR(20)    NULL, 
    `created_at`    TIMESTAMP      NOT NULL    DEFAULT CURRENT_TIMESTAMP, 
    `updated_at`    TIMESTAMP      NOT NULL    DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, 
     PRIMARY KEY (user_id)
);

-- Unique Index 설정 SQL - user_table(user_name)
CREATE UNIQUE INDEX UQ_user_table_1
    ON user_table(user_name);