考虑下表:
un_id avl_id avl_date avl_status
1738 6377398 2011-03-10 unavailable
1738 6377399 2011-03-11 unavailable
1738 6377400 2011-03-12 unavailable
1738 6719067 2011-03-12 unavailable
1738 6719351 2011-03-12 available
1738 6377401 2011-03-13 unavailable
1738 6377402 2011-03-14 unavailable
1738 6377403 2011-03-15 unavailable
1738 6377404 2011-03-16 available
1738 6719068 2011-03-16 unavailable
1738 6719352 2011-03-16 available
从以下查询获得:
SELECT
tbl_unit.un_id,
tbl_availability.avl_id,
tbl_availability.avl_date,
tbl_availability.avl_status
FROM
tbl_unit
INNER JOIN
tbl_availability ON
tbl_unit.un_id = tbl_availability.un_id
WHERE
tbl_availability.avl_active='True' AND
tbl_unit.un_active='True' AND
tbl_availability.avl_date >= '2011-03-10' AND
tbl_availability.avl_date
What I want is to GROUP BY un_id so that only the avl_status having the highest avl_id is displayed. i.e:
un_id avl_id avl_date avl_status
1738 6377398 2011-03-10 unavailable
1738 6377399 2011-03-11 unavailable
1738 6719351 2011-03-12 available
1738 6377401 2011-03-13 booked
1738 6377402 2011-03-14 booked
1738 6377403 2011-03-15 booked
1738 6719352 2011-03-16 available
我尝试添加GROUP BY和HAVING子句以及各种子查询,但我每次都失败了....
所有帮助表示赞赏! :) - 亚当。
答案 0 :(得分:0)
SELECT
tbl_unit.un_id,
tbl_availability.avl_id,
tbl_availability.avl_date,
tbl_availability.avl_status
FROM
tbl_unit
INNER JOIN
(select un_id, max(avl_id) as max_avl_id from tbl_availability group by un_id) T
on tbl_unit.un_id = T.un_id
INNER JOIN tbl_availability ON
T.max_avl_id = tbl_availability.avl_id
WHERE
tbl_availability.avl_active='True' AND
tbl_unit.un_active='True' AND
tbl_availability.avl_date >= '2011-03-10' AND
tbl_availability.avl_date
答案 1 :(得分:0)
试试这个:
SELECT
un_id,avl_status
FROM
(
SELECT
tbl_unit.un_id,
tbl_availability.avl_id,
tbl_availability.avl_date,
tbl_availability.avl_status
FROM
tbl_unit
INNER JOIN
tbl_availability ON
tbl_unit.un_id = tbl_availability.un_id
WHERE
tbl_availability.avl_active='True' AND
tbl_unit.un_active='True' AND
tbl_availability.avl_date >= '2011-03-10' AND
tbl_availability.avl_date
)
GROUP BY
un_id,avl_status
HAVING
avl_id=max(avl_id)