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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...cally, a lot of dbms have been quite poor when it comes to handling joins (MySQL being a particularly noteworthy example). So n+1 has, often, been notably faster than a join. And then there are ways to improve on n+1 but still without needing a join, which is what the original problem relates to.
H...
mysql check collation of a table
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Works for me in mysql 5.5.52. ...) ENGINE=InnoDB AUTO_INCREMENT=24 DEFAULT CHARSET=latin1 My guess is it may not show the collation if it is set to the default for the database in later versions of mysql/mariadb.
– Deve...
How to pull a random record using Django's ORM?
...e backend you're using." - any experience on diffrent DB backends? (sqlite/mysql/postgres)?
– kender
Jun 8 '09 at 9:37
4
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PDO Prepared Inserts multiple rows in single query
I am currently using this type of SQL on MySQL to insert multiple rows of values in one single query:
22 Answers
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How do I rename a column in a database table using SQL?
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This is not supported in MySQL, is it?
– ustun
Oct 21 '11 at 11:41
5
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How to execute a raw update sql with dynamic binding in rails
...d try accessing the underlying connection and using it's methods, e.g. for MySQL:
st = ActiveRecord::Base.connection.raw_connection.prepare("update table set f1=? where f2=? and f3=?")
st.execute(f1, f2, f3)
st.close
I'm not sure if there are other ramifications to doing this (connections left op...
Database development mistakes made by application developers [closed]
... exists--you should be using it.
It's quite common to see this failure on MySQL databases. I don't believe MyISAM supports it. InnoDB does. You'll find people who are using MyISAM or those that are using InnoDB but aren't using it anyway.
More here:
How important are constraints like NOT NULL...
c/c++如何判断指针无效？如NULL,0xcccccccc,0xfeeefeee,野指针等 - C/C++ -...
c/c++如何判断指针无效？如NULL,0xcccccccc,0xfeeefeee,野指针等c c++如何判断指针无效？不仅仅是NULL的判断，有时由于指针释放没有赋NULL，指针会变成野指针或诸如0xcccccccc,0xfeeefeee形式的无效指针，...c/c++如何判断指针无效？不仅仅是N...
Windows下如何调试NPAPI Plugins - 更多技术 - 清泛网 - 专注C/C++及内核技术
Windows下如何调试NPAPI Plugins关于NPAPI的介绍及开发方法请参考“开发”栏目下相关博文，这里主要讲述一下如何调试NPAPI Plugins，环境为Win7 + VS 2008。一、如何查看Plugins是否加载成功
Firefox和Chrome在浏览器地址栏输入 about:plugins，...
iOS开发如何提高 - 更多技术 - 清泛网 - 专注C/C++及内核技术
iOS开发如何提高许多人在博客和微信上咨询我iOS开发如何提高，经过一番思考之后，我能想到如下一些提高的办法，我个人也是通过这些方法来提高的。阅读博客...许多人在博客和微信上咨询我iOS开发如何提高，经过一番思考之...