SET @days = TIMESTAMPDIFF(DAY,'2021-06-01','2022-03-01');
SET @d = -1;
INSERT INTO `dw_learn_his_dt`
SELECT a.dt from
(
SELECT @d :=@d+1,ADDDATE('2021-06-01',@d) dt
from `dw_learn_his_dt`
WHERE @d<@days
) a
SET @days = TIMESTAMPDIFF(DAY,'2021-06-01','2022-03-01');
SET @d = -1;
INSERT INTO `dw_learn_his_dt`
SELECT a.dt from
(
SELECT @d :=@d+1,ADDDATE('2021-06-01',@d) dt
from `dw_learn_his_dt`
WHERE @d<@days
) a