Question

我会尽量保持清醒。

我有这3张表Customer，Link＆amp; Customer_link。

我正在使用以下查询从customer_no检索Customer列，该列具有表customer_no的{{1}}中未提供的值：

Customer_link

表SELECT c.customer_no FROM CUSTOMER c LEFT JOIN Customer_link cl ON c.customer_no = cl.customer_no WHERE cl.customer_no IS NULL包含以下列：

Customer_link

我尝试做的是，使用上面的查询从ID (generated automatically using a sequence) Customer_no (linked to Customer table) Link_no (linked to the Link table) Maker_id表中获取尚未添加到表customer_no的{{1}}（这是一个约束，因为Customer在表中不能有两次相同的Customer_link，这是唯一的。Customer_link也是如此。＆amp;从customer_no表中获取link_no的类似查询。

然后使用link_no＆amp;来自各自结果的Link＆amp;然后添加到表link_no（已经有一个函数，我将需要使用我在结果中得到的值调用）。

我需要在这里使用一个循环，这样我可以在将每个表中的值添加到表customer_no后更新结果，这样我就不会在尝试添加相同的{{1}时出错表格中两次或Customer_link。

使用光标是我在互联网上找到的一种方式。但这对我来说并不是很清楚。

所以我在这里尝试做的就是从Customer_link＆amp;获取未使用的customer_no的结果。来自customer_no＆amp;的Link_no在行1中插入值是表link_no＆amp;中的相应列。循环以更新结果＆amp;再次获取row1中的值，将它们作为参数添加到我调用的函数

中

Answer 1

我认为它不需要循环只需遵循这一步

1）将不在Customer_link中的所有customer_no插入 #temp 表

select c.customer_no into #temp from CUSTOMER c LEFT JOIN Customer_link cl on c.customer_no = cl.customer_no where cl.customer_no is null

2）将Customer_no插入Customer_link

insert into Customer_link(customer_no)
select customer_no from #temp

Answer 2

不需要循环。只需使用select作为插入源：

insert into customer_link (customer_no)
select c.customer_no 
from customer c 
  left Customer_link cl ON c.customer_no = cl.customer_no 
where cl.customer_no is null;

或者使用有时更快的NOT EXISTS查询：

insert into customer_link (customer_no)
select c.customer_no 
from customer c 
where not exists (select * 
                  from customer_link cl
                  where cl.customer_no = c.customer_no);

两个语句只会为customer_no列选择（并插入）唯一值（即没有重复项），假设customer_no是customer表中的主键。

Answer 3

customer_no中的第一个值是多少？我想这样的顺序。

此查询将仅按指定的顺序（rownum =1）添加返回的第一个值（ORDER BY c.customer_no）和customer_no，如果您不需要订购的值，只需删除ORDER BY子句。

INSERT INTO customer_link (customer_no)
SELECT  customer_no 
  FROM (
         SELECT c.customer_no 
           FROM CUSTOMER c 
      LEFT JOIN Customer_link cl 
             ON c.customer_no = cl.customer_no 
          WHERE cl.customer_no IS NULL
       ORDER BY c.customer_no
       ) sub
 WHERE rownum = 1

您可以在SQL Fiddle找到我准备的演示。

编辑：在您的问题发生更改后，我认为您正在寻找类似的内容：

  INSERT INTO customer_link (customer_no, link_no)
    SELECT  customer_no,
            your_function(customer_no)
      FROM (
             SELECT c.customer_no 
               FROM CUSTOMER c 
          LEFT JOIN Customer_link cl 
                 ON c.customer_no = cl.customer_no 
              WHERE cl.customer_no IS NULL
           ) sub

这将获取Customer_link中尚未存在的所有customer_no，并将它们放入该表中，并使用您的函数返回的link_no。

Answer 4

我终于找到了一种方法来使用游标。我将在这里提出解决方案，以便其他人可能需要帮助。

我创建了一个类型为Customer.Customer_no

的变量cust

cust Customer.Customer_no%type;

然后我创建了一个Cursor，以便能够将未使用的客户编号的值添加到

Cursor cr_cust IS select c.customer_no into cust from CUSTOMER c LEFT JOIN Customer_link cl on c.customer_no = cl.customer_no where cl.customer_no is null;

现在我用循环让这些都以这种方式工作

begin FOR i IN cr_cust LOOP --to loop through the rows cust := i.customer_no; --to add the value of corresponding row to the variable --cust IF j <= 5 THEN --this for getting the values from link table & assigning them to --variable so that the variables can be passed to the required function {code for assigning values to variables & the function calling go here} j:=j+1; --to get the next value in link table END IF; IF j > 5 THEN --exit if 5 customers have been added to the Customer_link table & --there is no need for more links to be fetched from link table EXIT; END IF; END LOOP; end

将列的第一个值检索到pl sql中的变量

4 个答案: