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CREATE TABLE tbl_users (
      user_code CHAR(6) NOT NULL PRIMARY KEY,
      user_name VARCHAR(20) NOT NULL,
      user_password CHAR(10) NOT NULL,
      user_level INTEGER NOT NULL,

      user_real_name VARCHAR(30),
      user_telephone VARCHAR(30),

      user_login_time TIMESTAMP,
      user_logout_time TIMESTAMP
)
