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Throw an error in a MySQL trigger
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As of MySQL 5.5, you can use the SIGNAL syntax to throw an exception:
signal sqlstate '45000' set message_text = 'My Error Message';
State 45000 is a generic state representing "unhandled user-defined exception".
Here is a mo...
从Sloodle看三维虚拟学习环境的发展趋势 - 资讯 - 清泛网 - 专注C/C++及内核技术
...游戏 ,吸引了越来越多的关注。现在的教育者也开始探索如何让学生在学习时也能像玩游戏一样沉浸其中。在游戏中需要解决一些交流、协作问题 ,这在学习系统中也会同样关注 ,因此很多学者也开始研究非正式学习领域内如何将...
MySQL get the date n days ago as a timestamp
In MySQL, how would I get a timestamp from, say 30 days ago?
3 Answers
3
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OnInitUpdate、OnUpdate、OnDraw与OnPaint - C/C++ - 清泛网 - 专注C/C++及内核技术
...情况下可能需要和框架直接发生作用，而在多视的情况下如何在视之间传递数据。
在使用菜单时大家会发现当一个菜单没有进行映射处理时为禁止状态，在多视的情况下菜单的状态和处理映射是和当前活动视相联系的，这...
Get records with max value for each group of grouped SQL results
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There's a super-simple way to do this in mysql:
select *
from (select * from mytable order by `Group`, age desc, Person) x
group by `Group`
This works because in mysql you're allowed to not aggregate non-group-by columns, in which case mysql just returns the first...
那些微信公众大号是如何赚钱的？ - 资讯 - 清泛网 - 专注C/C++及内核技术
那些微信公众大号是如何赚钱的？如今，微信公众号不仅是传递好文的平台，承载着万千运营者的兴趣和梦想，而且当粉丝量和文章阅读量高涨之后，随之而来的还有丰厚的经济效益。“你开公众号了吗？”不知从何时起，这个...
Difference between VARCHAR and TEXT in MySQL [duplicate]
When we create a table in MySQL with a VARCHAR column, we have to set the length for it. But for TEXT type we don't have to provide the length.
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How to get UTF-8 working in Java webapps?
...s" those characters.
To get UTF-8 working under Java+Tomcat+Linux/Windows+Mysql requires the following:
Configuring Tomcat's server.xml
It's necessary to configure that the connector uses UTF-8 to encode url (GET request) parameters:
<Connector port="8080" maxHttpHeaderSize="8192"
maxThreads...
MySQL Update Inner Join tables query
I have no idea what the problem is. Using MySQL 5.0 I get a compile error when attempting to run the following MySQL update query:
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MySQL: @variable vs. variable. What's the difference?
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MySQL has a concept of user-defined variables.
They are loosely typed variables that may be initialized somewhere in a session and keep their value until the session ends.
They are prepended with an @ sign, like this: @var
Yo...