条件语句 [英] conditional statements in derby

问题描述

它似乎 derby 不支持条件语句[如果]。我们如何写

It looks like derby doesn't support conditional statements [IF]. How do we write

if exists (select 1 from customers where name='somename') 
    update customers ...
else 
    insert into customers ...

Derby没有'replace into'的mysql。

in derby? Derby doesn't have 'replace into' of mysql either.

注意：我使用derby作为单元测试替换mysql [生产将使用mysql和单位-test将使用derby。

Note: I am using derby as unit-testing replacement for mysql [that is production will use mysql and unit-test will use derby].

推荐答案

http://db.apache.org/derby/docs/10.2/ref/rrefcasenullif.html#rrefcasenullif ？

   CASE
      WHEN 1 = 2 THEN 3
      WHEN 4 = 5 THEN 6
      ELSE 7
   END

也许你可以试试：

CASE
 WHEN  select 1 from customers where name='somename' = 1 THEN update...
ELSE  insert...
END

我不知道这是否可行，但似乎是一个开始。祝你好运！

I have no idea if that would work but it seems like a start. Good luck!

编辑：尝试了一些这些东西后...我不知道这是否真的会帮助你。它似乎不是你可以在SELECT和INSERT之间切换;它必须是一个或另一个和CASE进去。你想做什么可能或可能不可能...

edit: After trying a few of these things out...I don't know if this will really help you. It doesn't seem like you can fire switch between SELECT and INSERT; it has to be one or the other and the CASE goes inside. What you want to do may or may not be possible...

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