Question

我是DB2 dveloper的初学者

我要求通过加入两个表来显示下面的输出，以显示排除状态的结果。 enter image description here

水果清单

Name       Type
----       ----
apple      fruit
cranberry  fruit
blueberry  fruit
neamleaf   leaf
lemongrass leaf

过滤器：

Name       Type
----       ----
%berry     fruit
%grass     leaf
%root      vegetable

过滤结果，显示与like过滤器列表不匹配的水果

Name       Type
----       ----
apple      fruit
neamleaf   leaf

任何想法如何获得它？

Answer 1

我试过了：

create table master
  (type     varchar(10),
   name     varchar(25));
insert into master
  values ('fruit', 'apple'),  
         ('fruit', 'pineapple'),
         ('fruit', 'cranberry'),
         ('fruit', 'blueberry'),
         ('fruit', 'papaya'),
         ('fruit', 'orange'),
         ('leaf', 'neamleaf'),
         ('leaf', 'lemongrass'),
         ('leaf', 'orangegrass');

create table slave
  (type     varchar(10),
   search   varchar(25));
insert into slave
  values ('fruit', 'pple'), 
         ('fruit', 'berry'),
         ('leaf', 'grass');

select m.type, m.name
  from master m
where not exists
  (select * 
     from slave s
     where s.type = m.type
       and m.name like '%' || s.search || '%');

它提供了以下输出：

type    name
-----   --------
fruit   papaya
fruit   orange
leaf    neamleaf

<强>为什么
您描绘的输出让我感到困惑，因为我不希望您的查询首先工作。连接对我来说不起作用（也许该语法特定于LUW，但由于select拼写为slect，我怀疑你的例子是手工键控而不是剪切和粘贴）。当我尝试使用适用于我的语法的方法时，我得到了两行用于木瓜，两行用于橙色，另外一行用于其他每个水果。这是因为使用m.type = s.type的联接为每个水果提供了两行（slave中每个'水果'行一个），然后m.name not like '%'||s.search||'%'过滤掉不匹配的行结果集中的搜索字段。

让我们看看未经过滤的结果集：

m.type    m.name      s.type    s.search    filtered/output
------    ----------- --------- ----------- ---------------
fruit     apple       fruit     pple        xxxx filtered
fruit     apple       fruit     berry            output
fruit     pineapple   fruit     pple        xxxx filtered
fruit     pineapple   fruit     berry            output
fruit     cranberry   fruit     pple             output 
fruit     cranberry   fruit     berry       xxxx filtered
fruit     blueberry   fruit     pple             output 
fruit     blueberry   fruit     berry       xxxx filtered
fruit     papaya      fruit     pple             output 
fruit     papaya      fruit     berry            output 
fruit     orange      fruit     pple             output 
fruit     orange      fruit     berry            output
leaf      neamleaf    leaf      grass            output 
fruit     lemongrass  leaf      grass       xxxx filtered
fruit     orangegrass leaf      grass       xxxx filtered

DB2如何从两个表中获取不同的多行

1 个答案: