大约有 19,000 项符合查询结果(耗时:0.0227秒) [XML]

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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...
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mysql check collation of a table

... 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...
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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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CMake使用教程 - C/C++ - 清泛网 - 专注C/C++及内核技术

...中找到这个手册对应的代码。 1、Step1。 (如果不知道如何使用cmake,以及如何使用编译产生的Turorial.exe,可先看下前面“CMake使用步骤”的说明,它以Step4为例详细介绍了使用过程,Step1的配置可能不够完全,比如无法运行make...
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创业者如何发现开放却未知的秘密 - 资讯 - 清泛网 - 专注C/C++及内核技术

创业者如何发现开放却未知的秘密所谓开放却未知的秘密,其实就在用户手上,在用户口中,就在数据里面。最近几篇专栏一直在围绕需求这个主题展开,从第一篇的人性,第二篇的最美投资往往在眨眼之间,到第三篇的敬畏街...
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How do I rename a column in a database table using SQL?

... 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...
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如何跟程序员谈一场没有Bug的恋爱 - 杂谈 - 清泛网 - 专注C/C++及内核技术

如何跟程序员谈一场没有Bug的恋爱现在越来越多的妹子把恋爱目标锁定在程序员上,原因无他:呆萌又多金。但如何和程序员相处一直是个问题,这篇文章就教你如何优(xin)雅(j 现在越来越多的妹子把恋爱目标锁定在程序...
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AppInventor如何扫二维码?扫码结果如何与Web进行交互? - App Inventor 2 ...

Q:请问扫二维码怎么实现? [hide]A:使用“条码扫描器”组件:https://www.fun123.cn/reference/ ... html#BarcodeScanner       属性“使用外部扫描”设置为假,其他没有啥要注意的。就调用一下扫描方法,就能使用摄像头扫...
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技术人员如何创业《三》- 合伙人的分工 - 资讯 - 清泛网 - 专注C/C++及内核技术

技术人员如何创业《三》- 合伙人的分工中国梦我们习主席上台后就大大倡导。国家领导人有他们的中国梦,创业者也怀揣着创业的梦想。我们张罗好产品就要准备风风火火的大干一番了。 “中国梦”我们习主席上台后就大大...