mysql+redis+memcached

<div id="mainContent"> <div class="forFlow"> <div id="post\_detail">  <div id="topics"> <div class="post"> <h1 class="postTitle"> <a id="cb\_post\_title\_url" class="postTitle2" href="https://www.cnblogs.com/hnlmy/p/9997515.html">mysql+redis+memcached</a> </h1> <div class="clear"></div> <div class="postBody"> <div id="cnblogs\_post\_body" class="blogpost-body"><h1 id="autoid-0-0-0">数据库</h1> <h2 id="autoid-0-0-0">数据库设计</h2> <div class="cnblogs\_code"><div class="cnblogs\_code\_toolbar"><span class="cnblogs\_code\_copy"><a href="javascript:void(0);" onclick="copyCnblogsCode(this)" title="复制代码"><img src="https://my.oschina.net//common.cnblogs.com/images/copycode.gif" alt="复制代码"></a></span></div> <pre><span style="color: #000000;"> a. 单表 b. FK（单表；一张表存储时，如果有重复出现的字段为了防止硬盘的浪费，所以做一个FK；去掉FK变成单表（这样子访问速度快了）） c. M2M（多对多关系）

到底是什么关系？单选的下拉框</span>/radio FK；多选下拉框/checkbox M2M </pre>

1        调薪：
2            id  price  time  员工ID

思路二：三张表员工表： id name salary

1         调薪：
2            id  price  time 
3            
4            
5        员工调薪表：
6            id   uid   sid</span></pre>

1        用户表：
2            id          name        部门id
3            </span>1           x1          1
4            2           x2          1
5            3           x3          1
6            4           x4          1
7            5           x5          1</pre>

1        select </span>* <span style="color: #0000ff;">from</span> depart left join userinfo on userinfo.did = depart.id    7<span style="color: #000000;">
2    
3        select </span>* <span style="color: #0000ff;">from</span> userinfo inner join depart on userinfo.did = depart.id   5<span style="color: #000000;">
4    
5        select </span>* <span style="color: #0000ff;">from</span> depart inner join userinfo on userinfo.did = depart.id   5</pre>

1            select </span>* <span style="color: #0000ff;">from</span> xxx  <span style="color: #0000ff;">for</span><span style="color: #000000;"> update;
2            
3            update ...
4            
5            commit;
6        
7        django:
8                
9            with trancation.automic:
10                User.objects.filter().select_for_update()</span></pre>

1    </span>-<span style="color: #000000;"> 联合索引：多列组成一个索引
2    </span>- 联合唯一索引：多列组成一个索引 +<span style="color: #000000;"> 唯一
3        例如：
4            name  email  pwd 
5            
6     命中索引遵循最左前缀的原则： name、name  email、name pwd、name  email  pw</span></pre>

1为什么索引快？
2    因为在索引结构中讲述按照B</span>+来进行存放的数据。</pre>

1    在django中的应用：
2        models.Users.objects.filter(id</span>=2).using(<span style="color: #800000;">'</span><span style="color: #800000;">default</span><span style="color: #800000;">'</span><span style="color: #000000;">)
3        models.Users.objects.filter(id</span>=2).using(<span style="color: #800000;">'</span><span style="color: #800000;">db1</span><span style="color: #800000;">'</span><span style="color: #000000;">)
4g. limit 
5    select </span>* <span style="color: #0000ff;">from</span> tb where name=<span style="color: #800000;">'</span><span style="color: #800000;">alex</span><span style="color: #800000;">'</span> limit 1<span style="color: #000000;">;
6    
7h. 缓存
8    将常用数据读取到redis中（缓存），读取速度快。
9    </span></pre>

<div class="cnblogs\_code\_toolbar"><span class="cnblogs\_code\_copy"><a href="javascript:void(0);" onclick="copyCnblogsCode(this)" title="复制代码"><img src="https://my.oschina.net//common.cnblogs.com/images/copycode.gif" alt="复制代码"></a></span></div></div> <h2 id="autoid-5-0-0">char和varchar的区别。</h2> <div class="cnblogs\_code"> <pre><span style="color: #000000;">char是定长，不变的。 varchar是变长，可变的。</span></pre> </div> <h2 id="autoid-6-0-0">视图、触发器、存储过程、函数</h2> <div class="cnblogs\_code"> <pre><span style="color: #000000;">视图：视图是虚拟表或逻辑表，它被定义为具有连接的SQL SELECT查询语句。因为数据库视图与数据库表类似，它由行和列组成，因此可以根据数据库表查询数据。其内容由查询定义。但是，视图并不在数据库中以存储的数据值集形式存在，行和列数据来自由定义视图的查询所引用的表，并且在引用视图时动态生成。简单的来说视图是由其定义结果组成的表；触发器：触发器，是一个表数据的变更后通过触发器来修改与之相关联的其他表的数据，保证数据的一致性。使用触发器可以定制用户对表进行【增、删、改】操作时前后的行为，注意：没有查询</span></pre> </div> <div class="cnblogs\_code"> <pre><span style="color: #000000;">存储过程是存储在数据库目录中的一坨的声明性SQL语句。 Java，Python，PHP等应用程序可以调用存储过程。</span></pre> </div> <div class="cnblogs\_code"> <pre>mysql自定义函数就是实现程序员需要sql逻辑处理，参数是IN参数,含有RETURNS字句用来指定函数的返回类型，而且函数体必须包含一个RETURN value语句。</pre> </div> <p> </p></div><div id="MySignature"></div> <div class="clear"></div> <div id="blog\_post\_info\_block"> <div id="BlogPostCategory">分类: <a href="https://www.cnblogs.com/hnlmy/category/1346509.html" target="\_blank">mysql</a></div> <div id="EntryTag">标签: <a href="https://www.cnblogs.com/hnlmy/tag/mysql/">mysql</a></div> <div id="blog\_post\_info"><div id="green\_channel"> <a href="javascript:void(0);" id="green\_channel\_digg" onclick="DiggIt(9997515,cb\_blogId,1);green\_channel\_success(this,'谢谢推荐！');">好文要顶</a> <a id="green\_channel\_follow" onclick="follow('9dd4be1f-fb20-4ca9-9d43-08d5866282ce');" href="javascript:void(0);">关注我</a> <a id="green\_channel\_favorite" onclick="AddToWz(cb\_entryId);return false;" href="javascript:void(0);">收藏该文</a> <a id="green\_channel\_weibo" href="javascript:void(0);" title="分享至新浪微博" onclick="ShareToTsina()"><img src="https://my.oschina.net//common.cnblogs.com/images/icon\_weibo\_24.png" alt=""></a> <a id="green\_channel\_wechat" href="javascript:void(0);" title="分享至微信" onclick="shareOnWechat()"><img src="https://my.oschina.net//common.cnblogs.com/images/wechat.png" alt=""></a> </div> <div id="author\_profile"> <div id="author\_profile\_info" class="author\_profile\_info"> <a href="http://home.cnblogs.com/u/hnlmy/" target="\_blank"><img src="https://my.oschina.net//pic.cnblogs.com/face/1353629/20180808085333.png" class="author\_avatar" alt=""></a> <div id="author\_profile\_detail" class="author\_profile\_info"> <a href="http://home.cnblogs.com/u/hnlmy/">hnlmy</a><br> <a href="http://home.cnblogs.com/u/hnlmy/followees">关注 - 11</a><br> <a href="http://home.cnblogs.com/u/hnlmy/followers">粉丝 - 4</a> </div> </div> <div class="clear"></div> <div id="author\_profile\_honor"></div> <div id="author\_profile\_follow"> <a href="javascript:void(0);" onclick="follow('9dd4be1f-fb20-4ca9-9d43-08d5866282ce');return false;">+加关注</a> </div> </div> <div id="div\_digg"> <div class="diggit" onclick="votePost(9997515,'Digg')"> <span class="diggnum" id="digg\_count">0</span> </div> <div class="buryit" onclick="votePost(9997515,'Bury')"> <span class="burynum" id="bury\_count">0</span> </div> <div class="clear"></div> <div class="diggword" id="digg\_tips"> </div> </div> <script type="text/javascript"> currentDiggType = 0; </script></div> <div class="clear"></div> <div id="post\_next\_prev"><a href="https://www.cnblogs.com/hnlmy/p/9997466.html" class="p\_n\_p\_prefix">« </a> 上一篇：<a href="https://www.cnblogs.com/hnlmy/p/9997466.html" title="发布于2018-11-21 20:03">复习-网路编程和并发编程</a><br></div> </div>

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mysql+redis+memcached

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