执行以下 Oracle 查询时出错答案

【问题标题】：Error while executing the below Oracle query执行以下 Oracle 查询时出错
【发布时间】：2020-12-25 15:00:27
【问题描述】：

我正在尝试将下面的 Sybase 查询转换为 Oracle 查询。

update Student set st.age = (case when st.promoted != 'fail' then 1 
else (select sc1.age from school sc1 where st.id = sc1.id ) END)
from Student st ,School sc
where st.id = sc.id
AND st.status in('1','7','2','5')
AND st.currentClass = sc.currentClass 
AND st.currentCource = sc.currentCource ;

但我尝试在转换后执行以下 Oracle 查询，但出现以下错误。

update Student st set st.age = (select (case when st.promoted != 'fail' 
then 1 
else (select sc1.age from school sc1 where st.id = sc1.id ) END) 
from School sc   
where st.id = sc.id
AND st.status in('1','7','2','5')
AND st.currentClass = sc.currentClass 
AND st.currentCource = sc.currentCource )
where exists 
   (select 1 from School sc1
where st.id = sc1.id
AND st.status in('1','7','2','5')
AND st.currentClass = sc1.currentClass 
AND st.currentCource = sc1.currentCource);

查询返回：ORA-01427 单行子查询返回多于一行。有谁请帮忙

【问题讨论】：

标签： sql oracle join sql-update subquery

【解决方案1】：

Oracle 不支持 update 语句中的 joins。您可以改用相关子查询 - 连接所做的只是过滤，所以 exists 应该这样做：

update student st 
set st.age = 20 
where 
    st.status in(1, 7, 2, 5)
    and exists (
        select 1 
        from school sc 
        where 
            st.id = sc.id  
            and st.currentClass = sc.currentClass  
            and st.currentCource = sc.currentCource 
    )

【讨论】：

使用 case 语句更新了值，现在您的查询需要进行任何更改

【解决方案2】：

您可以使用密钥保留视图来编写此更新，如下所示：

UPDATE (SELECT st.age as age, 
                st.promoted,
                sc.age,
               st.currentClass,
               sc.currentClass,
               st.currentCource,
               sc.currentCource
          FROM Student st INNER JOIN
               School sc
         ON (st.id = sc.id AND st.currentClass = sc.currentClass AND st.currentCource = sc.currentCource)
         WHERE st.status IN ('1','7','2','5'))
   SET age = CASE WHEN st.promoted != 'fail' THEN 1 ELSE sc.age END;

你可以参考这个post 我已经回答了如何将 Sybase 更新查询转换为 Oracle。

【讨论】：

【解决方案3】：

update Student st set st.age = case when st.promoted != 'fail'
                                    then 1 
                                    else (select sc1.age from school sc1
                                          where st.id = sc1.id )
                                    end
where exists 
   (select 1 from School sc1
where st.id = sc1.id
AND st.status in('1','7','2','5')
AND st.currentClass = sc1.currentClass 
AND st.currentCource = sc1.currentCource);

【讨论】：

我已经更新了20个case语句，现在如何转换
我已经尝试过同样的方法来转换这个 sybase 查询，但没有工作：你能帮我update Product set pd.age = (case when pd.exittime!= null then 1 else ( case when pd.queue = dp.queue then (select (sysdate - pd.exittime) from department dp1 where pd.id = dp1.id ) else 2 END) END) from Product pd,department dp where pd.id > 1 AND pd.id = dp.id AND pd.status in('1','7','2','5') AND pd.currentstatus = dp.currentstatus AND pd.activity= dp.activity;
您需要指定别名：update Product pd set...
让我们continue this discussion in chat.
您仍在尝试使用新查询中的联接进行更新 - 您尚未转换它。