CREATE TABLE ps_districts
(
    ps_id        BIGINT NOT NULL,
    districts_id BIGINT NOT NULL
);

ALTER TABLE ps_districts
    ADD CONSTRAINT uc_ps_districts_districts UNIQUE (districts_id);

ALTER TABLE ps_districts
    ADD CONSTRAINT fk_psdis_on_district FOREIGN KEY (districts_id) REFERENCES district (id);

ALTER TABLE ps_districts
    ADD CONSTRAINT fk_psdis_on_p_s FOREIGN KEY (ps_id) REFERENCES ps (id);