MySQL的组由基于另一场中的基团（未在表中）

考虑下面表中的最高值的字段：MySQL的组由基于另一场中的基团（未在表中）


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

这是从下面的查询获得：


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

 我想要的是GROUP BY un_id，以便只显示具有最高avl_id的avl_status。即：

 
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

我已经尝试添加GROUP BY和HAVING子句和各种子查询，但我每次都失败....

所有帮助感激！ :) - 亚当。

来源

2011-03-11 Adam

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

来源

2011-03-11 15:12:11 zsong

看起来不错，但也不能令人信服：＃1054 - 未知列 'T.avl_id' 在 '关于条款' – Adam 2011-03-11 15:19:40

哎呀，我看到了问题，需要添加T.avl_id到子查询SELECT子句... – Adam 2011-03-11 15:21:23

仍然无法正常工作，我也尝试了INNER JOIN tbl_availability ON T.max_avl_id = tbl_availability.avl_id – Adam 2011-03-11 15:22:54

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)

来源

2011-03-11 16:32:08

MySQL的组由基于另一场中的基团（未在表中）

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