mysql - 无法使用 group by 查询获取 MySQL 中的某些字段

Question

我有以下查询(并尝试了它的很多变体) :

select housedata.housecode, housedata.name, min((pergroup + (perguest *  GREATEST((2 - guests_included),0)))) as mincalculated 
from housedata
inner join availabilitydata 
where housedata.housecode = availabilitydata.housecode 
and  datediff(departure, arrival) = 7 group by housedata.housecode

这工作正常，但我需要表可用性数据中的更多字段。当我尝试添加这些 MySQL 提示时:

[42000][1055] Expression #4 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'houses.availabilitydata.arrival' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

我可以将该字段添加到分组依据中，但随后我会得到多个结果，因为可用性数据是多行。

如何将其限制为每栋房屋一行，即从中获取 min((pergroup + (perguest * GREATEST((2 - guest_included),0)))) 的行。

表格:

create table availabilitydata
(
  arrival              date        not null,
  departure            date        not null,
  housecode            varchar(32) not null,
  pergroup             float       null,
  pergroupexcldiscount float       null,
  perguest             float       null,
  guests_included      tinyint     null,
  primary key (housecode, arrival, departure)
);

create table housedata
(
  housecode       varchar(32) not null
    primary key,
  name            tinytext    null
);

数据应如下所示，但添加了日期列:

344323  Wienerwaltz 680.530029296875
434300  Wald    882.7899780273438
943843  Chalet Miquel   630.8300170898438

Answer 1

尝试这样:

select h.housecode
     , hh.name
     , pergroup + (perguest *  GREATEST((2 - guests_included),0)) as mincalculated
     -- select any column from a (availabilitydata)
from housedata h
inner join availabilitydata a on a.housecode = h.housecode 
where (a.housecode, a.arrival, a.departure) = (
    select a2.housecode, a2.arrival, a2.departure
    from availabilitydata a2
    where a2.housecode = h.housecode
      and datediff(a2.departure, a2.arrival) = 7
    order by a2.pergroup + (a2.perguest *  GREATEST((2 - a2.guests_included),0)) asc
    limit 1
)

在相关子查询中，您将获得计算值最小的行的主键(a.housecode, a.arrival, a.departure)。在外部查询中，您仅选择 availabilitydata 中具有相同主键的行。

请注意，如果两行具有相同的计算最小值，您将同时获得它们。如果您不需要两者，您应该在 ORDER BY 子句中定义您想要的一个(例如，添加完整的主键):

order by a2.pergroup + (a2.perguest *  GREATEST((2 - a2.guests_included),0)) asc
    , a2.arrival
    , a2.departure

更新

上述解决方案似乎表现不佳。但如果您的版本支持窗口函数，您还可以使用以下查询:

select *
from (
    select housedata.housecode
         , housedata.name
         , pergroup + (perguest *  GREATEST((2 - guests_included),0)) as mincalculated
         , row_number() over (
             partition by housedata.housecode
             order by pergroup + (perguest *  GREATEST((2 - guests_included),0)) asc
         ) rn
         , availabilitydata.arrival
         -- select any other column from availabilitydata
    from housedata
    inner join availabilitydata on housedata.housecode = availabilitydata.housecode 
    where datediff(departure, arrival) = 7
) x
where rn = 1