SQL Track Open Appointment

Question

我是SQL的初学者，我正在开发一个查询，为每个Provider（Employee）生成Open Appointment Time Slot。任何人都可以帮助以下查询？非常感谢你！

安排表样本数据：

ScheduleNum |  ProvNum (Provider) | SchedDate | StartTime | EndTime
          1 |                   3 |  7/1/2017 |    8:00AM |  9:00 AM
          2 |                   3 |  7/1/2017 |   10:00AM | 11:00 AM
          3 |                   4 |  7/1/2017 |    8:00AM |  9:00 AM
          4 |                   4 |  7/1/2017 |   12:00PM |  1:00 PM
          5 |                   4 |  7/1/2017 |    3:00PM |  4:00 PM

打开约会查询表预期结果：

ProvNum (Provider) | SchedDate | avail_start_dt_time| avail_end_dt_time
                 3 | 7/1/2017  |            9:00 AM |          10:00 AM
                 4 | 7/1/2017  |            9:00 AM |          12:00 PM
                 4 | 7/1/2017  |            1:00 PM |           3:00 PM

查询我正在处理。

SELECT
    avail.schedulenum
  , avail.provnum
  , avail.start_at  as avail_start_dt_time
  , avail.end_at    as avail_end_dt_time
  , avail.on_dt     as just_date_no_time
  , avail.starttime as prov_start_time
  , avail.endtime   as prov_end_time
FROM (
  SELECT
        dts.num, dts.on_dt, dts.start_at, dts.end_at, s.provnum, s.starttime, s.stoptime
  FROM (
        /* generates 1000, 10 minute "slots", starting at a variable date */
        SELECT
              schedulenum + 1 as num
            , DATE_ADD(INTERVAL (slots.num * 10) MINUTE) start_at
            , DATE_ADD(INTERVAL ((slots.num+ 1) * 10) MINUTE) end_at
        FROM (
              /* generates 1000 rows 0 to 999 */
              SELECT hundreds.digit * 100 + tens.digit * 10 + ones.digit AS num
              FROM (
                    SELECT 0 AS digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL
                    SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
                   ) ones
              CROSS JOIN (
                    SELECT 0 AS digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL
                    SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
                         ) tens
              CROSS JOIN (
                    SELECT 0 AS digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL
                    SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
                         ) hundreds
              ) slots
        ) dts
  INNER JOIN schedule s ON s.starttime < dts.end_at AND s.stoptime > dts.start_at
  ) avail
WHERE schedulenum IS NULL