Oracle更新字段格式

UPDATE TMP_GJ_TEST_ZD_N2 A SET A.XH=
    (SELECT X.XH FROM TMP_GJ_TEST_ZD_N3 X
        WHERE X.OFFER_SPEC_ID=A.OFFER_SPEC_ID)
                    WHERE EXISTS(SELECT 1 FROM TMP_GJ_TEST_ZD_N3 X
                                    WHERE X.OFFER_SPEC_ID=A.OFFER_SPEC_ID);
COMMIT;