text: --TABLE USERS--
  CREATE  TABLE users (
    username VARCHAR2(45) NOT NULL ,
    password VARCHAR2(45) NOT NULL ,
    enabled NUMBER(3) DEFAULT 1 NOT NULL ,
    PRIMARY KEY (username));
  ------------------------------------------------------------------------------------  
  --TABLE USER_ROLES--
  CREATE TABLE user_roles (
    user_role_id number(10) NOT NULL,
    username varchar2(45) NOT NULL,
    role varchar2(45) NOT NULL,
    PRIMARY KEY (user_role_id),
    CONSTRAINT uni_username_role UNIQUE (role,username)
   ,
    CONSTRAINT fk_username FOREIGN KEY (username) REFERENCES users (username));
  
  -- Generate ID using sequence and trigger
  CREATE SEQUENCE user_roles_seq START WITH 1 INCREMENT BY 1;
  
  CREATE OR REPLACE TRIGGER user_roles_seq_tr
   BEFORE INSERT ON user_roles FOR EACH ROW
   WHEN (NEW.user_role_id IS NULL)
  BEGIN
   SELECT user_roles_seq.NEXTVAL INTO :NEW.user_role_id FROM DUAL;
  END;
  /
  
  CREATE INDEX fk_username_idx ON user_roles (username);