选择具有优先级值的非重复行答案

【问题标题】：SELECT non duplicated rows with priority value选择具有优先级值的非重复行
【发布时间】：2020-05-04 10:40:54
【问题描述】：

我有一个表，其中包含带有测量值的行。对于同一个批次 id，可以指定多个度量。我想在以下条件下得到正确的值：

如果给定批次只有一行，则度量有效
如果有多行相同类型，则度量无效，返回的类型应为“无效”，值 = 0
如果有不止一行不同类型（一个“已获得”和一个“已验证”），则返回的行必须是“已验证”行

样本数据：

create table measures (
  batch  int,
  type   varchar(24),
  value int
);

insert into measures select 01,'Verified',10;
insert into measures select 02,'Acquired',34;
insert into measures select 03,'Verified',22;
insert into measures select 03,'Verified',24;
insert into measures select 04,'Verified',32;
insert into measures select 04,'Acquired',34;
insert into measures select 05,'Acquired',42;
insert into measures select 05,'Acquired',44;

样本输出：

01   Verified   10
02   Acquired   34
03   Invalid    0
04   Verified   32
05   Invalid    0

【问题讨论】：

你的第一个条件似乎与其他两个条件有关。
这是一种非常奇怪的方式来编写 INSERT 语句。 VALUES 子句有什么问题？
您使用的是哪个DBMS 产品？ “SQL”只是一种查询语言，而不是特定数据库产品的名称。请为您正在使用的数据库产品添加tag。 Why should I tag my DBMS
db引擎是SQL SERVER，我已经加了tag。

标签： sql sql-server select duplicates

【解决方案1】：

你的逻辑有点难以理解。你可以用条件聚合做你想做的事。它认为逻辑是：

select batch,
       (case when count(*) = 1 then max(type)
             when min(type) = max(type) then 'Invalid'
             else coalesce(max(case when type = 'Verified' then 'Verified' end), 'Invalid')
        end) as type,
       (case when count(*) = 1 then max(value)
             when min(type) = max(type) then 0
             else coalesce(max(case when type = 'Verified' then value end), 0)
        end) as value
from measures m
group by batch;

【讨论】：

【解决方案2】：

使用windows函数：

;WITH CountTypesPerBatch AS
(
    SELECT batch, type, value,
           COUNT(CASE WHEN type = 'Verified' THEN 1 END) 
              OVER (PARTITION BY batch) AS verified,
           COUNT(CASE WHEN type = 'Acquired' THEN 1 END) 
              OVER (PARTITION BY batch) AS acquired,
           ROW_NUMBER() OVER (PARTITION BY batch 
                              ORDER BY IIF(type='Verified',1, 2)) seq
    FROM measures
)
SELECT DISTINCT batch, 
       CASE 
          WHEN verified > 1 OR acquired > 1 THEN 'invalid' 
          WHEN verified = 1 THEN 'verified'
          ELSE 'acquired'
       END,
       CASE 
          WHEN verified > 1 OR acquired > 1 THEN 0
          ELSE value
       END
FROM CountTypesPerBatch
WHERE seq = 1

Demo here

【讨论】：