sqlserver查看哪段时间不存在数据

SELECT
a.dt AS '时间',
ISNULL(b.ODPI_EM_Key, '0') AS '数据'
FROM
(
SELECT
dateadd(d, number, '2018-12-01') dt
FROM
master..spt_values
WHERE
type = 'p'
AND dateadd(d, number, '2018-12-01') <= '2020-11-30'
) a
LEFT JOIN V_ODP_Info b ON a.dt = b.ODPI_Date