Question

我试图找出如何从另一个表中更新一个表，这是PL / SQL查询的结果。

这是我尝试做的事情：

update c
set c.customerType = n.newType
from customers c
join 
    (select 
         c.customerNumber, c.customerType, 
         case when c.customerType = 'business' and count(s.subCode) = 1 
                 then 'small business' 
                 else null  
         end as NewType
     from customers c
     join subscribers s on c.customerNumber = s.customerNumber
     group by c.customerNumber, c.customerType) n on c.customerNumber = n.customerNumber;

请注意，表客户如下所示：

customerNumber   customerType
------------------------------
1                business
4                business
2                private
3                private

表n（子查询）给出以下结果：

customerNumber   customerType   newType
1                business       null
4                business       small business
3                private        null
2                private        null

我在做什么错了？

P.S最终，我只想在newType不为null的情况下用newType更新customerType。

谢谢

Answer 1

尝试这样

UPDATE customers
SET customerType = ( SELECT N.newType 
                        FROM
                        (
                            SELECT c.customerNumber, c.customerType, CASE WHEN c.customerType = 'business' AND count(s.subCode) = 1 THEN 'small business' ELSE NULL END AS NewType
                            FROM customers c1 JOIN subscribers s ON c1.customerNumber = s.customerNumber
                            GROUP BY c1.customerNumber, c.customerType
                        ) N
                    );

Answer 2

you to write plsql like below
=============================
   declare
     cursor c1 is
        select c.customerNumber, c.customerType, 
             case when c.customerType = 'business' and count(s.subCode) = 1 then 'small 
              business'
             else null end as NewType
        from customers c,subscribers s
        where c.customerNumber = s.customerNumber
        group by c.customerNumber, c.customerType;
begin
for cur in c1 loop
     update customers set customer_type = cur.NewType
     where customerNumber = cur.customerNumber;
     commit;
end loop;
end;

Answer 3

您使用相关子查询。不过，就您的情况而言，我认为所有工作都可以在外部where子句中完成：

update customers c
    set c.customerType = 'small business'
    where c.customerType = 'business' and
          (select count(s.subcode)
           from subscribers s
           where s.customerNumber = c.customerNumber
          ) = 1;

如果客户在subcode表中恰好有一个subscribers，则会将“业务”客户更新为“小型企业”。

来自另一个子查询表的更新表-“ SQL命令未正确结束”

3 个答案: