尝试子查询时出现不明确的列名错误

Posted 2023-02-16

【中文标题】尝试子查询时出现不明确的列名错误

【英文标题】：Getting an Ambiguous column name error when trying to subquery

【发布时间】：2021-03-05 01:31:03

【问题描述】：

提示是假设风险“1”设施每年至少需要进行 3 次类型检查。显示 2013 年未能满足此要求且至少有 1 次 Canvass 类型检查失败的设施。显示设施名称以及 2013 年有多少 Canvass 检查。提示：使用子查询

这是我的代码

SELECT DBAName, COUNT(*)
FROM FoodInspectionOriginal, Organization
WHERE Risk = 1 AND [Inspection Type] IN (SELECT [Inspection Type] FROM FoodInspectionOriginal WHERE [Inspection Type] = 'Canvass' AND [Inspection Date] = Year(2013))
GROUP BY DBAName;

我得到这是输出

消息 209，第 16 级，状态 1，第 3 行

不明确的列名“风险”。

【问题讨论】：

错误意味着 FoodInspectionOriginal 和 Organization 表具有相同的列名：Risk

进化——没有人应该使用old-style joins。

【参考方案1】：

我只会使用聚合。假设表foodinspectionoriginal的表结构如下：

dbaname           -- name of the facility
inspection_date   
inspection_type   -- "Canvass", ...
inspection_status -- "successful", "failed"

查询可以表述如下：

select dbaname,
    sum(case when inspection_type = 'Canvass' and inspection_status = 'failed' then 1 else 0 end) as cnt_failed_canvass
from foodinspectionoriginal
where 
    risk = 1 
    and inspection_date >= '20130101' 
    and inspection_date <  '20140101'
group by dbaname 
having 
    count(*) < 3 
    and sum(case when inspection_type = 'Canvass' and inspection_status = 'failed' then 1 else 0 end) > 0