sql - 在 SQL 中选择特定的不同列

Question

我正在尝试创建一个 select 语句，以便它在一列上执行特定的不同操作。我正在努力使每个 id 中没有多个水果。如果一个 id 下有多个水果，我只想使用 1 个批准的水果，而不是腐烂的水果。如果该 id 下只有 1 个水果，请使用它。

SELECT id, fruit, fruitweight, status 
  FROM myfruits

Raw data from current select    

    id |  fruit  | fruitweight | status
    1  |  apple  |      .2     | approved
    1  |  apple  |      .8     | approved
    1  |  apple  |      .1     | rotten
    1  |  orange |      .5     | approved
    2  |  grape  |      .1     | rotten
    2  |  orange |      .7     | approved
    2  |  orange |      .5     | approved  

约束后应该如何格式化

    id |  fruit  | fruitweight | status
    1  |  apple  |      .2     | approved
    1  |  orange |      .5     | approved
    2  |  grape  |      .1     | rotten
    2  |  orange |      .7     | approved

我可以按照 select distinct id,fruit,fruitweight,status from myfruits 的方式做一些事情， 但这只会在所有列都相同的情况下删除重复项。

Answer 1

具有聚合和 row_number 的 CTE。

declare @YourTable table (id int, fruit varchar(64), fruitweight decimal(2,1),status varchar(64))
insert into @YourTable
values
(1,'apple',0.2,'approved'),
(1,'apple',0.8,'approved'),
(1,'apple',0.1,'rotten'),
(1,'orange',0.5,'approved'),
(2,'grape',0.1,'rotten'),
(2,'orange',0.7,'approved'),
(2,'orange',0.5,'approved')


;with cte as(
select
    id
    ,fruit
    ,fruitweight = min(fruitweight)
    ,[status]
    ,RN = row_number() over (partition by id, fruit order by case when status = 'approved' then 1 else 2 end)
from 
    @YourTable
group by
    id,fruit,status)

select
    id
    ,fruit
    ,fruitweight
    ,status
from
    cte
where RN = 1

另一种方法，没有聚合...假设您想要 first fruightweight

;with cte as(
select
    id
    ,fruit
    ,fruitweight 
    ,[status]
    ,RN = row_number() over (partition by id, fruit order by case when status = 'approved' then 1 else 2 end, fruitweight)
from 
    @YourTable)

select
    id
    ,fruit
    ,fruitweight
    ,status
from
    cte
where RN = 1