Question

我有一个名为列表的日期列表，人们可以注册参与预订。

listings
id |    date    | capacity
1    2010-01-01   3
2    2010-01-02   1
3    2010-02-02   2

bookings
id | listing_id | name
1    1            Chris
2    1            Steve
3    1            Allen
4    2            Tracy

我想要做的是查询，该查询仅根据预订返回打开的列表。

查询只返回id = 3的列表。因为它没有预订且容量为2。

Sample query which won't work:
SELECT
    *
FROM
    listings
HAVING COUNT(
             SELECT * FROM bookings WHERE listings.id=bookings.listing_id
            ) < capacity

感谢任何帮助。

Answer 1

SELECT *
FROM listings
WHERE capacity > (SELECT count(*) 
                  FROM bookings 
                  WHERE listings.id=bookings.listing_id)

Answer 2

SELECT
    listings.id,
    max(listings.date),
    max(listings.capacity)
FROM listings
left join bookings on listings.id = bookings.listing_id
group by listings.id
having COUNT(bookings.listing_id) < max(listings.capacity)

Answer 3

*我自己，我会加入然后算一下：

SELECT COUNT(*) as count 
FROM listings, bookings 
WHERE listings.id=bookings.listing_id 
AND count < listings.capacity 
GROUP by listings.id

我没有测试过，但这是一般的想法！

MySQL - 在哪里/有计数＆gt; COLUMNNAME

3 个答案: