CREATE TABLE A 
    (
    ID          INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    NAME        VARCHAR(255),
    DESCRIPTION VARCHAR(255)
    );

CREATE TABLE B
    (
    ID          INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    NAME        VARCHAR(255),
    DESCRIPTION VARCHAR(255)
    );
              
CREATE TABLE MAP_A_B 
    (
    A_ID               INTEGER NOT NULL,
    B_ID               INTEGER NOT NULL
    );
                
ALTER TABLE MAP_A_B
    ADD CONSTRAINT  FK_MAP_A_B__A_ID
    FOREIGN KEY     (A_ID)
    REFERENCES      A (ID);

ALTER TABLE MAP_A_B
    ADD CONSTRAINT  FK_MAP_A_B__B_ID
    FOREIGN KEY     (B_ID)
    REFERENCES      B (ID);