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<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span 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class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br></pre></td><td class="code"><pre><span class="line">Python学习框架</span><br><span class="line">1.注释：#、''' '''、 """ """</span><br><span class="line">2.标识符</span><br><span class="line">3.关键字</span><br><span class="line">4.数据类型：int、float、complex、bool、str</span><br><span class="line"> 查看类型type()，判断是否是指定类型isinstance(数据,类型)</span><br><span class="line">5.缩进</span><br><span class="line">6.print函数和input函数</span><br><span class="line">7.声明一个或多个变量、变量互换:a,b=b,a</span><br><span class="line">8.运算符： a.数学运算符：+、-、*、/、//、%、**</span><br><span class="line"> b.比较运算符：>、<、>=、<=、!=、== (补充is)</span><br><span class="line"> c.逻辑运算符：and、or、not</span><br><span class="line"> d.赋值运算符：=、+=、-=、*=、/=、//=、%=、**=</span><br><span class="line"> 优先级：数字>比较>逻辑>赋值</span><br><span class="line">9.数字类型：a.int</span><br><span class="line"> b.float</span><br><span class="line"> c.bool</span><br><span class="line"> d.complex</span><br><span class="line">10.字符串：分类：a.普通字符</span><br><span class="line"> b.转义字符 \</span><br><span class="line"> c.编码字符 \u****</span><br><span class="line"> d.字符编码：chr(编码值) - 获取字符</span><br><span class="line"> ord(字符) - 获取编码</span><br><span class="line"> 内建函数：1）字符串.capitalize()</span><br><span class="line"> 2）字符串.center(width,fillchar)</span><br><span class="line"> 3）字符串1.count(字符串2)</span><br><span class="line"> 4) 字符串1.endwith(字符串2,start,end)</span><br><span class="line"> 5) 字符串.expandtabs(tabsize)</span><br><span class="line"> 6) 字符串1.find(字符串2,beg,end)</span><br><span class="line"> 7）字符串1.index(字符串2,beg,end)</span><br><span class="line"> 8）字符串1.isalnum()</span><br><span class="line"> 9）字符串.isalpha()</span><br><span class="line"> 10）字符串.isdigit()</span><br><span class="line"> 11) 字符串.idlower()</span><br><span class="line"> 12) 字符串.isnumeric()</span><br><span class="line"> 13）字符串.isspace()</span><br><span class="line"> 14) 字符串.istitle()</span><br><span class="line"> 15) 字符串.isupper()</span><br><span class="line"> 16) 字符串1.join(字符串2)</span><br><span class="line"> 17) len(字符串)</span><br><span class="line"> 18) 字符串1.ljust(width,fillchar)</span><br><span class="line"> 19) 字符串.lower()</span><br><span class="line"> 20) 字符串.lstrip()</span><br><span class="line"> 21) max()</span><br><span class="line"> 22) min()</span><br><span class="line"> 23) 字符串.replace(old,new,max)</span><br><span class="line"> 24）字符串1.rfind(字符串2,beg,end)</span><br><span class="line"> 25) 字符串.rjust(width,fillchar)</span><br><span class="line"> 26) 字符串.rstrip()</span><br><span class="line"> 27) 字符串1.split(字符串2,num)</span><br><span class="line"> 28) 字符串1.startswith(字符串2,beg,end)</span><br><span class="line"> 29) 字符串.strip()</span><br><span class="line"> 30) 字符串.swapcase</span><br><span class="line"> 31) 字符串.title()</span><br><span class="line"> 32) 字符串.upper()</span><br><span class="line"> 33) 字符串.zfill(width)</span><br><span class="line"> 34) 字符串.isdecimal()</span><br><span class="line"> 获取字符串：字符串[下标]、字符串[开始下标：结束下标：步长]</span><br><span class="line"> 字符串运算符:+、*、>、<、==、！=、>=、<=</span><br><span class="line"> in 和 not in 操作</span><br><span class="line"> len(序列)</span><br><span class="line"> 格式字符串：占位符 % (值1, 值2，...)</span><br><span class="line"> 占位符:%s、%d、%f或%nf、%c、%u、%o、%x、%X、%e、%E、%g、%G</span><br><span class="line"> 类型转换：int(数据)、float(数据)、bool(数据)、str()</span><br><span class="line">11.语法：a.条件语句:什么时候使用，语法，执行过程，</span><br><span class="line"> if结构、if-else结构、if-elif-else结构、</span><br><span class="line"> 值1 if 表达式 else 值2</span><br><span class="line"> b.循环语句:for循环和while循环</span><br><span class="line"> range() 注意：最后的取不到</span><br><span class="line"> continue、break、break...else</span><br><span class="line">12.列表list：a.定义:可变,有序</span><br><span class="line"> b.字面量:[2,3,6...]</span><br><span class="line"> c.获取元素：列表[下标]、列表[开始下标,结束下标,步长]、for循环遍历</span><br><span class="line"> d.增：列表.append(元素)</span><br><span class="line"> 列表.insert(下标,元素)</span><br><span class="line"> 删：del 列表(下标)</span><br><span class="line"> 列表.remove(元素)</span><br><span class="line"> 列表.pop(下标)</span><br><span class="line"> 坑：1)遍历列表元素删不全：切片删</span><br><span class="line"> 2)遍历列表下标下标越界删不全：下标元素删除的下标值不懂；不删的下标+1</span><br><span class="line"> e.改：列表[下标] = 新值</span><br><span class="line"> f.运算符：+、*、比较运算符、in和not in</span><br><span class="line"> g.类型转换:list()</span><br><span class="line"> h.取长度：len(列表)</span><br><span class="line"> i.max(序列)、min(序列)、sum(序列)</span><br><span class="line"> j.内建函数：1) list.append(对象)</span><br><span class="line"> 2）list.count(元素)</span><br><span class="line"> 3) list.extend(序列)</span><br><span class="line"> 4) list.index(元素)</span><br><span class="line"> 5）list.insert(index,对象)</span><br><span class="line"> 6）list.pop([index=-1])</span><br><span class="line"> 7）list.remove(元素)</span><br><span class="line"> 8）list.reverse()</span><br><span class="line"> 9) list.sort(cmp=None,key=None,reverse=False)</span><br><span class="line"> 10) list.clear()</span><br><span class="line"> 11) list.copy()</span><br><span class="line">13.元祖(tuple):a.定义(不可变,有序)</span><br><span class="line"> b.字面量：(2,4,6),</span><br><span class="line"> ()空元祖、(3，)只有一个元素的元祖</span><br><span class="line"> c.获取元素:1)元祖[下标]</span><br><span class="line"> 2)元素[:]</span><br><span class="line"> 3)遍历</span><br><span class="line"> 4)变量1,变量2..=元祖</span><br><span class="line"> 变量1,*变量2 =元祖</span><br><span class="line"> d.相关运算:+、*、in/not in、len()、max()、min()、sum()</span><br><span class="line"> e.排序：sorted(序列) - 不管什么序列排完都是产生一个新的列表</span><br><span class="line"> 列表.sort() - 修改原列表中元素的排序</span><br><span class="line">14.字典(dict):a.定义:可变，无序</span><br><span class="line"> b.字面量：{key1:value1,key2:value2...}</span><br><span class="line"> key:唯一,不可变</span><br><span class="line"> c.什么时候使用字典</span><br><span class="line"> d.获取值:字典[key]-key不存在会报错</span><br><span class="line"> 字典.get(key)-key不存在会取得None</span><br><span class="line"> 字典.get(key,值1)-key不存在会取得值1</span><br><span class="line"> 遍历字典取得key值,利用key值取value</span><br><span class="line"> 遍历字典的values(),获取所有值(不建议使用)</span><br><span class="line"> 遍历字典的items()，获取所有key和value(不建议使用)</span><br><span class="line"> 增/改加值：字典[key]=值</span><br><span class="line"> 删:del 字典[key]</span><br><span class="line"> 字典.pop(key)</span><br><span class="line"> f.相关运算:==、！=、in、not in、len()、max()、min()</span><br><span class="line"> g.相关方法:1）字典.clear()</span><br><span class="line"> 2) 字典.copy() - 产生一个新的字典</span><br><span class="line"> 3) 字典.fromkeys(序列,值)</span><br><span class="line"> 4）字典.keys()</span><br><span class="line"> 5) 字典.values()</span><br><span class="line"> 6）字典.items()</span><br><span class="line"> 7）字典.setdefault(key,value=None)</span><br><span class="line"> 8) 字典.update(字典2)</span><br><span class="line">15.集合(set):a.定义：可变,无序,元素唯一</span><br><span class="line"> b.字面量:{元素1,元素2,元素3,...}</span><br><span class="line"> c.查元素:遍历</span><br><span class="line"> 增加元素:集合.add(元素)</span><br><span class="line"> 集合.update(元素)</span><br><span class="line"> 集合.remove()</span><br><span class="line"> d.运算：&、|、-、^</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">.进制:二进制：0b/B+二进制数;转换成二进制数:bin(其他进制)</span><br><span class="line"> 八进制: 0o/O+八进制数;转换成八进制数:oct(其他进制)</span><br><span class="line"> 十六进制: 0x/X+十六进制数;转换成十六进制数:hex(其他进制)</span><br><span class="line"> 原码:符号位(0代表正数，1代表负数)+真值</span><br><span class="line"> 反码：正数的反码还是原码；负数的反码符号位不变，其他位取反(1和0互换)</span><br><span class="line"> 补码：正数的补码还是原码；负数的补码是反码+1</span><br><span class="line"> 为什么存补码(计算机中只有加法器,没有加法器)</span><br><span class="line"> 位运算：&(与1与判断奇偶)、|(与1或置1)、~、^(判断两个数是否相同)、>>(除以2的n次方)、<<</span><br></pre></td></tr></table></figure>
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<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br></pre></td><td class="code"><pre><span class="line"># vim编辑器之神</span><br><span class="line">### 配置vimrc配置</span><br><span class="line">在shell中可以通过 `vim ~/.vimrc` 或者 `vim /etc/vimrc` 打开vimrc文件对vim进行配置。在这个文件中可以进行很多和vim相关的配置，常用的如下（如果对其他配置感兴趣的可以自己百度）：</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">### 常用操作</span><br><span class="line">#### 1.模式切换</span><br><span class="line">我们可以将vim分为命令模式、编辑模式和末行模式三种 </span><br><span class="line">**命令模式：**进入vim的时候vim是处于命令模式状态下的，这个时候输入内容不会出现在编辑区 (最末什么都没有)</span><br><span class="line"></span><br><span class="line">**末行模式：**在命令模式下输入冒号，让vim进入末行模式。在末行模式的冒号后面可以输入相关的一些指令进行相关操作 (最后有一个冒号)</span><br><span class="line"></span><br><span class="line">**编辑模式：**在命令模式下按'i'进入编辑模式。在编辑模式下可以对文件内容进行编辑 (最后 --INSERT-- 或者 --插入--) </span><br><span class="line"></span><br><span class="line">####2.保存和退出</span><br><span class="line">在末行模式下输入相应的指令可以对编辑区的内容进行保存和退出vim界面 </span><br><span class="line">**w** -- 只保存(类似快捷键ctr+s) </span><br><span class="line">**q** -- 退出（在编辑区的内容全部都保存的情况下才有效） </span><br><span class="line">**wq** -- 保存并退出 </span><br><span class="line">**q!** -- 强制退出（不保存修改信息） </span><br><span class="line"></span><br><span class="line">####3.光标操作 </span><br><span class="line">以下光标操作都是在命令模式下输入的 </span><br><span class="line">**^(shift+6)** -- 移动到行首 </span><br><span class="line">**$(shift+4)** -- 移动到行尾 </span><br><span class="line">**G(shift+g)** -- 移动到文件末尾</span><br><span class="line">**行号G** -- 移动到指定行,例如:30G, 让光标直接跳转到行号是30的那一行</span><br><span class="line">**gg** -- 移动到文件开头 </span><br><span class="line"></span><br><span class="line">####4.文本操作 </span><br><span class="line">以下操作不带冒号的是在命令模式下输入，前面有冒号代码后面的内容是在末行模式下输入 </span><br><span class="line">**dd** -- 删除光标所在的行 </span><br><span class="line">**数字dd** -- 从光标所在行开始往后面开始删，删除指定数量行内容 </span><br><span class="line">**:%d** -- 删除所有 </span><br><span class="line"></span><br><span class="line">**yy** -- 复制光标所在的行 </span><br><span class="line">**数字yy** -- 从光标所在行开始复制指定行数的内容 </span><br><span class="line">**p** -- 将复制的内容粘贴到光标所在的位置 </span><br><span class="line">**u** -- 撤销 </span><br><span class="line">**ctr+r** -- 反撤销 </span><br><span class="line"></span><br><span class="line">**:%!sort** -- 对内容排序(将一行内容看出一个字符串然后按照字符串大小进行排序) </span><br><span class="line">**：/正则表达式** -- 搜索匹配正则表达式的内容，按回车回到命令模式后按n往前查找，按N往后查找 </span><br><span class="line">**:/查找对象[/gice]** -- 搜索匹配正则表达式的内容，按回车回到命令模式后按n往前查找，按N往后查找 </span><br><span class="line">注意：正则表达式除了表示次数的符号前需要加\，别的和python是一样的。例如：</span><br><span class="line">'''</span><br><span class="line">：/\d\{2} -> 查找两个数字</span><br><span class="line">：/a\+ -> 查找a出现一次或者多次</span><br><span class="line">'''</span><br><span class="line"></span><br><span class="line">**:1,$s/被替换对象/替换内容/参数** -- 将正则表达式匹配到的内容替换成指定内容 </span><br><span class="line"></span><br><span class="line"> - g: 全局匹配 </span><br><span class="line"> - i: 忽略大小写 </span><br><span class="line"> - c: 替换时需要提示 </span><br><span class="line"> - e: 忽略错误</span><br></pre></td></tr></table></figure>
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class="line">392</span><br><span class="line">393</span><br><span class="line">394</span><br><span class="line">395</span><br><span class="line">396</span><br><span class="line">397</span><br><span class="line">398</span><br><span class="line">399</span><br><span class="line">400</span><br></pre></td><td class="code"><pre><span class="line">数据库排名：</span><br><span class="line">Oracle(关系型) </span><br><span class="line">MySQL(关系型) </span><br><span class="line">SQLServer(关系型) </span><br><span class="line">PostgreSQL(关系型) </span><br><span class="line">MongoDB(非关系数据库) </span><br><span class="line">DB2(关系型) </span><br><span class="line">Redis(非关系数据库) </span><br><span class="line">ElasticSearch(非关系数据库) </span><br><span class="line"></span><br><span class="line">行（记录）</span><br><span class="line">列(字段)</span><br><span class="line"></span><br><span class="line">关系型数据库：想</span><br><span class="line"></span><br><span class="line">SQL语句(结构化查询语言) </span><br><span class="line">DDL(数据定义语言)： create / drop / alter </span><br><span class="line">DML(数据操作语言 - Data Manipulation Language): insert / delete / update / select </span><br><span class="line">DCL(数据控制语言): grant / revoke </span><br><span class="line"></span><br><span class="line">-- 注意: SQL中大小写不敏感（大写和小写是一样的）; 每条SQL语句必须以分号结束</span><br><span class="line"></span><br><span class="line">-- 一.DDL - 主要提供数据库和表的创建、删除和修改 </span><br><span class="line">-- 0. 删除数据库: drop database 数据库名;</span><br><span class="line">DROP DATABASE school; -- 直接删除指定数据库</span><br><span class="line">DROP DATABASE if EXISTS school; -- 如果指定的数据库存在就删除数据库</span><br><span class="line"></span><br><span class="line">-- 1.创建数据库: create database 数据库名;</span><br><span class="line">create database school; -- 直接创建指定数据库</span><br><span class="line">CREATE database if not EXISTS school; -- 当指定数据库不存在的时候才创建数据库</span><br><span class="line">create database if not EXISTS school default charset utf8; -- 创建数据库的时候设置字符集编码方式为utf8,让数据库支持中文数据的存储</span><br><span class="line"></span><br><span class="line">-- 2.使用/切换数据库: use 数据库名;</span><br><span class="line">use school;</span><br><span class="line"></span><br><span class="line">-- 3.新建表: create table if not exists 表名(字段名1 类型1, 字段2 类型2,...);</span><br><span class="line">-- 注意： a. 表名一般需要加前缀't'或者'tb' b.字段用来确定表中要存储哪些数据，字段名随便命名但是不能是关键字 c.数据类型必须是MySQL支持的数据类型</span><br><span class="line">-- 常用数据类型: int-整数, char(size)-定长字符串, varchar(size)-不定长字符串, text-字符串, bit-布尔, date-日期</span><br><span class="line">CREATE TABLE if not EXISTS t_student(stuid int, stuname varchar(20), gender bit, birth date); </span><br><span class="line"></span><br><span class="line">-- 新建表并且添加约束: create table if not exists 表名(字段名1 类型1 约束1, 字段2 类型2 约束2,...);</span><br><span class="line">-- 常见约束: not null - 不为空, default - 设置默认值, unique - 值唯一, primary key - 主键约束 </span><br><span class="line">-- 主键约束: 主键的值可以确定列表中唯一一条记录(通过一个主键值可以找到表中的唯一一条记录)</span><br><span class="line">-- 注意: auto_increment只针对主键有效,并且主键的类型是整型;</span><br><span class="line">CREATE TABLE if not EXISTS t_student</span><br><span class="line">(</span><br><span class="line">stuid int not null auto_increment, </span><br><span class="line">stuname varchar(20) not null, </span><br><span class="line">gender bit DEFAULT 1, </span><br><span class="line">birth date,</span><br><span class="line">PRIMARY KEY(stuid) -- 将字段stuid作为当前表的主键（设置主键可以间接约束这个字段的值是唯一的）</span><br><span class="line">);</span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">-- 4.删除表: DROP TABLE if EXISTS 表名;</span><br><span class="line">DROP TABLE if EXISTS t_student; </span><br><span class="line">-- 清空表中的数据: TRUNCATE TABLE 表名;</span><br><span class="line">TRUNCATE TABLE t_student;</span><br><span class="line"></span><br><span class="line">-- 5.修改表</span><br><span class="line">-- 5.1 添加列: alter TABLE 表名 add COLUMN 字段名 字段类型 约束;</span><br><span class="line">alter TABLE t_student add COLUMN score FLOAT(8,2) DEFAULT 0;</span><br><span class="line"></span><br><span class="line">-- 5.2 删除列: alter TABLE 表名 drop COLUMN 字段名;</span><br><span class="line">alter TABLE t_student drop COLUMN gender;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- 二、DML(数据操作语言) - 主要针对数据库中数据的增、删、改、查</span><br><span class="line">-- 1.增(添加数据/记录)</span><br><span class="line">-- 1.1插入数据/记录: insert into 表名 values(值1, 值2, 值3,....) - 依次给指定表中的字段赋值</span><br><span class="line">INSERT into t_student VALUES(100, '张三', 0, '2019-9-23');</span><br><span class="line"></span><br><span class="line">-- 1.2插入数据/记录: insert into 表名(字段名1,字段名2,...) values(值1, 值2,...) -以指定的顺序给指定的字段赋值 </span><br><span class="line">INSERT into t_student(stuname, birth) VALUES("小花", date(now())); -- 一次插入一条记录</span><br><span class="line"></span><br><span class="line">-- 一次插入多条记录</span><br><span class="line">INSERT into t_student(stuname, birth) VALUES</span><br><span class="line">("小花", date(now())),</span><br><span class="line">('小明', '2018-9-8'),</span><br><span class="line">('路飞', '1999-12-16'),</span><br><span class="line">('佐助', '2000-10-12');</span><br><span class="line"></span><br><span class="line">-- 值的问题: sql中是数字对应的值直接写，字符串需要使用引号引起来，bit类型的值只有0或者1, 时间可以用内容是满足时间格式字符串也可以是通过时间函数获取的值</span><br><span class="line">-- 时间函数: now() - 当前时间 date(now()) - 当前日期 year(now()) - 当前年 month(now()) - 当前月 .... </span><br><span class="line"></span><br><span class="line">-- 2.删（删除数据/记录） </span><br><span class="line">-- delete from 表名; - 删除指定表中所有记录</span><br><span class="line">DELETE FROM t_student;</span><br><span class="line"></span><br><span class="line">-- delete from 表名 where 条件语句; - 删除满足条件的记录 </span><br><span class="line">-- SQL中的条件语句: =(判断是否相等), <>(不等于,和python中的!=功能一样), >, <, >=, <=</span><br><span class="line">DELETE FROM t_student WHERE stuid=100; -- 删除t_student表中stuid的值等于100的记录 </span><br><span class="line">DELETE FROM t_student WHERE stuname='小花'; -- 删除t_student表中stuname的值等于'小花'的记录</span><br><span class="line">DELETE FROM t_student WHERE stuid<108; -- 删除t_student表中stuid的值小于'小花'的记录 </span><br><span class="line"></span><br><span class="line">-- 3.改(修改数据/记录) </span><br><span class="line">-- update 表名 set 字段1=新值1, 字段2=新值2,...; - 将指定表中所有行的指定列/字段的值赋值为新值</span><br><span class="line">UPDATE t_student set birth='1999-10-1', gender=1;</span><br><span class="line"></span><br><span class="line">-- update 表名 set 字段1=新值1, 字段2=新值2,... where 条件语句; -将表中满足条件的行中指定字段的值赋值为新值 </span><br><span class="line">UPDATE t_student set gender=0 WHERE stuname='小花';</span><br><span class="line"></span><br><span class="line">-- 通配符%: 表示任意个数的任意字符（包括0个）</span><br><span class="line">UPDATE t_student set birth='2000-01-01' WHERE stuname LIKE '小%'; -- 修改stuname是以'小'开头的行对应的birth的值</span><br><span class="line">UPDATE t_student set birth='2111-01-01' WHERE stuname LIKE '%小%'; </span><br><span class="line">-- 统配符_: 表示一个任意字符</span><br><span class="line">UPDATE t_student set birth='2444-01-01' WHERE stuname LIKE '小_'; -- 修改stuname只有两个字符，并且第一个字符是‘小’对应的行的birth的值</span><br><span class="line">-- 注意: 通配符只针对字符串有效! </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- 4.查(获取数据)</span><br><span class="line">-- 4.1直接查询</span><br><span class="line">-- select * from 表名; - 获取指定表中所有行和所有的列(所有数据)</span><br><span class="line">SELECT * FROM t_student;</span><br><span class="line"></span><br><span class="line">-- select 字段名1,字段名2,... from 表名; - 获取指定表中所有行指定的列 </span><br><span class="line">SELECT stuname,stuid FROM t_student; </span><br><span class="line"></span><br><span class="line">-- select * from 表名 where 条件; - 获取指定表中所有满足条件的行所有列的数据 </span><br><span class="line">SELECT * FROM t_student WHERE stuid>115; </span><br><span class="line"></span><br><span class="line">-- 4.2列重命名</span><br><span class="line">-- select 字段1 as 新字段1, 字段2 as 新字段2,... from 表名;</span><br><span class="line">-- 注意： 这儿的as可以省略</span><br><span class="line">SELECT stuid as '学号', stuname, gender as '性别' FROM t_student; -- 对查询结果中的stuid和gender字段进行重命名</span><br><span class="line"></span><br><span class="line">-- 4.3对查询结果重新赋值(一般针对布尔数据)</span><br><span class="line">-- select if(字段名,值1,值2) from 表名; -查询指定字段，并且判断字段对应的值是0还是1，如果是1结果为值1，否则为值2</span><br><span class="line">-- 注意: 这儿的if的用法是MySQL专有的</span><br><span class="line">-- MySQL写法: if(字段, 新值1, 新值2)</span><br><span class="line">SELECT stuname,if(gender,'男','女') as '性别' FROM t_student; </span><br><span class="line">-- 通用写法: case 字段 when 值 then 新值1 else 新值2 end</span><br><span class="line">SELECT case gender WHEN 1 THEN '男' ELSE '女' END as '性别' FROM t_student;</span><br><span class="line"></span><br><span class="line">-- 4.4对列进行合并</span><br><span class="line">-- select concat(字段1,字段2,...) from 表名;</span><br><span class="line">SELECT CONCAT(stuname,stuid) as 'name_id' FROM t_student;</span><br><span class="line">SELECT CONCAT(stuname,':',stuid) as 'name_id' FROM t_student;</span><br><span class="line">-- 注意: 数字和字符串数据可以合并，bit类型的数据不可以合并</span><br><span class="line">-- SELECT CONCAT(stuname,':',gender) as 'name_id' FROM t_student; </span><br><span class="line"></span><br><span class="line">-- 4.5模糊查询 - 查询的时候时候通过like条件来指定查询对象</span><br><span class="line">-- sql中支持逻辑运算符and(逻辑与运算)和or(逻辑或运算)，not(逻辑非)</span><br><span class="line">SELECT * FROM t_student WHERE stuname like '%飞%' or not stuid < 110; </span><br><span class="line"></span><br><span class="line">-- 4.6排序(先按之前的任何语法进行查询在排序)</span><br><span class="line">-- select * from 表名 order by 字段; - 对查询结果按照指定字段的值进行升序排序 </span><br><span class="line">-- select * from 表名 order by 字段 asc; - 对查询结果按照指定字段的值进行升序排序 </span><br><span class="line">-- select * from 表名 order by 字段 desc; - 对查询结果按照指定字段的值进行降序排序</span><br><span class="line">SELECT * FROM t_student ORDER BY gender; -- 按性别升序排序</span><br><span class="line">SELECT * FROM t_student ORDER BY stuid ASC; -- 按学号升序排序</span><br><span class="line">SELECT * FROM t_student ORDER BY stuid DESC; -- 按学号降序排序</span><br><span class="line"></span><br><span class="line">-- 排序的时候可以通过在order by的后边加多个字段，进行联排。排序的时候前面的字段的优先级高些</span><br><span class="line">SELECT * FROM t_student ORDER BY gender ASC, stuid DESC; -- 先按性别进行升序排序，然后再按学号降序排序。 </span><br><span class="line"></span><br><span class="line">-- 4.7限制 </span><br><span class="line">-- select * from 表名 limit N; -- 获取查询结果的前N条记录</span><br><span class="line">SELECT * FROM t_student LIMIT 3; -- 获取查询结果的前3条记录</span><br><span class="line"></span><br><span class="line">-- select * from 表名 limit M offset N; -- 对查询结果跳过前N条数据，取M条数据出来 </span><br><span class="line">SELECT * FROM t_student LIMIT 3 offset 4; -- 跳过前4数据，然后取3条数据</span><br><span class="line">-- =================================sql基础补充===============================</span><br><span class="line">-- 1.条件语句的写法</span><br><span class="line">-- 在SQL中可以通过 `where 条件语句`来对操作对象进行筛选 - 筛选 </span><br><span class="line">-- a. 比较运算符： =, <>, >, <, >=, <=</span><br><span class="line">-- 注意: 判断一个字段的值是否为空不用使用=和<>, 而是使用`is null` 和 `is not null`</span><br><span class="line">SELECT addr FROM t_student;</span><br><span class="line">SELECT stuname FROM t_student WHERE addr is NULL; -- 判断是否为NULL（空）</span><br><span class="line">SELECT stuname FROM t_student WHERE addr=''; -- 判断是否是空串</span><br><span class="line">-- b. 逻辑运算符: and, or, not </span><br><span class="line">-- c. where 字段名 between 值1 and 值2 -- 筛选指定的字段的值在值1和值2之间</span><br><span class="line">SELECT stuname,birth FROM t_student WHERE birth BETWEEN '1990-1-1' AND '1999-12-31'; </span><br><span class="line">-- d. where 字段名 in 集合 -- 筛选出字段值是集合中的元素;(集合是使用括号括起来里面多个值)</span><br><span class="line">SELECT * FROM t_student WHERE stuname in ('小花', '小明', '路飞'); </span><br><span class="line">-- e. like操作 </span><br><span class="line"></span><br><span class="line">-- 2.数据类型 </span><br><span class="line">-- varchar(size): 不定长字符串，size决定的是最大长度</span><br><span class="line">-- char(size): 定长字符 </span><br><span class="line">-- text: 不限长度(最大是255个字符)</span><br><span class="line">-- int/tinyint(-128~127)</span><br><span class="line">-- FLOAT(size,d)/DOUBLE(size,d) - 这儿的size和d的值都有约束效果</span><br><span class="line">-- bit: 只有0和1两个值</span><br><span class="line">-- date/datetime/time: 值可以是时间函数的结果，也可以时间字符串；计算或者是比较的时候内部是按时间处理的</span><br><span class="line">UPDATE t_student SET tel='1367819230';</span><br><span class="line">ALTER TABLE t_student ADD COLUMN intro VARCHAR(10);</span><br><span class="line">SELECT * FROM t_student; </span><br><span class="line"></span><br><span class="line">-- 3.去重 </span><br><span class="line">SELECT DISTINCT addr FROM t_student; </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- ========================添加约束=========================</span><br><span class="line">-- 1.创建表的时候添加约束</span><br><span class="line">CREATE TABLE if not EXISTS t_college</span><br><span class="line">(</span><br><span class="line">collid int, </span><br><span class="line">collname VARCHAR(20) NOT NULL, -- 创建表的时候添加约束</span><br><span class="line">website VARCHAR(1024), </span><br><span class="line">intro VARCHAR(200),</span><br><span class="line">PRIMARY KEY(collid)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 2.通过添加约束索引的方式添加约束 </span><br><span class="line">-- a.添加约束</span><br><span class="line">-- alter table 表名 add constraint 索引名 约束 (字段名);</span><br><span class="line">-- 说明: 索引名 - 自己随便命名，用来指向当前添加的约束； 约束 - 需要添加的约束(支持唯一约束、主键约束和外键约束)</span><br><span class="line"></span><br><span class="line">ALTER TABLE t_college ADD CONSTRAINT con_website UNIQUE (website); </span><br><span class="line">-- 给t_college表中的website添加unique约束，约束索引为con_website</span><br><span class="line"></span><br><span class="line">-- b.删除约束</span><br><span class="line">-- alter table 表名 drop index 约束索引;</span><br><span class="line">ALTER TABLE t_college DROP index con_website;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- ====================外键和E.R图================</span><br><span class="line">-- 1.什么是外键：表中的某个字段的值是根据其他表中主键的值来确定的。那么这个字段就是外键 </span><br><span class="line">-- 1.1 多对一的外键的添加： 将外键添加到多的一方对应的表中 </span><br><span class="line">-- 一对一的外键的添加： 将外键随便添加到哪一方，同时添加值唯一约束 </span><br><span class="line">-- 多对多的外键的添加： 关系型数据库中，两张表没法实现多多的关系，需要一个中间表。(中间表有两个外键分别参照多多的两个表的主键)</span><br><span class="line">-- 1.2 怎么添加外键： </span><br><span class="line"></span><br><span class="line">-- a.添加外键对应的字段 </span><br><span class="line">alter TABLE tb_student add COLUMN collid int;</span><br><span class="line"></span><br><span class="line">-- b.给设计好的外键对应的字段添加外键约束</span><br><span class="line">-- alter table 表1 add constraint 索引名 foreign key (字段1) references 表2 (字段2); </span><br><span class="line">-- - 将表1中的字段1设置为外键，并且让这个外键的值参照表2中的字段2</span><br><span class="line">ALTER TABLE tb_student ADD CONSTRAINT fk_collid_stu </span><br><span class="line">FOREIGN KEY (collid) </span><br><span class="line">REFERENCES tb_college (collid);</span><br><span class="line"></span><br><span class="line">-- c. 删除外键约束 </span><br><span class="line">-- alter table 表名 drop foreign key 外键索引名; - 可以删除外键约束，但是外键索引还存在；需要额外的把索引删掉</span><br><span class="line">-- 注意: 删除外键约束的时候直接删除约束的索引无效，必须先将约束删掉，然后再删除索引.</span><br><span class="line">ALTER TABLE tb_student DROP FOREIGN KEY fk_collid_stu;</span><br><span class="line">ALTER TABLE tb_student DROP INDEX fk_collid_stu; </span><br><span class="line"></span><br><span class="line">-- d. 多对多的外键约束</span><br><span class="line">-- 添加学生的外键约束 </span><br><span class="line">ALTER TABLE tb_score ADD CONSTRAINT fk_stuid_score </span><br><span class="line">FOREIGN KEY (stuid) </span><br><span class="line">REFERENCES tb_student (stuid);</span><br><span class="line"></span><br><span class="line">-- 添加课程的外键约束</span><br><span class="line">ALTER TABLE tb_score ADD CONSTRAINT fk_couid_score </span><br><span class="line">FOREIGN KEY (couid) </span><br><span class="line">REFERENCES tb_course (couid);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- ==================查询的高级操作================= </span><br><span class="line">-- 1.聚合：max()/min()/sum()/avg()/count()</span><br><span class="line">-- SELECT 聚合函数(字段) FROM 表名WHERE 条件; -- 按条件多表查询指定字段数据，然后将查询结果做相应的聚合运算。聚合运算的结果是最后结果 </span><br><span class="line">SELECT mark FROM tb_score; -- 获取tb_score表中的所有分数值</span><br><span class="line">SELECT max(mark) as maxmark FROM tb_score; -- 获取tb_score表中所有分数的最大值</span><br><span class="line">SELECT min(mark) FROM tb_score; </span><br><span class="line">SELECT sum(mark) FROM tb_score; </span><br><span class="line">SELECT avg(mark) FROM tb_score WHERE scoreid>=123; -- 计算平均值的时候如果参与运算的对象的值为NULL,那么这个数据不会参与计算</span><br><span class="line">SELECT count(mark) FROM tb_score WHERE mark>=90;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- 2.分组 </span><br><span class="line">-- SELECT 字段操作 FROM 表名 WHERE 条件 GROUP BY(字段2); </span><br><span class="line">-- 将指定表中满足条件的记录按照字段2的进行分组(值是一样的在一个组里面), 然后再讲每个分组作为整体按照指定字段进行指定聚合操作</span><br><span class="line">-- 求每个学生的平均成绩</span><br><span class="line">SELECT stuid,avg(mark) FROM tb_score WHERE scoreid <= 115 GROUP BY(stuid) ;</span><br><span class="line">-- 注意:a.字段操作的位置除了分组字段不用聚合，其他字段都必须聚合 b.分组的时候where要放到分组前对需要分组的数据进行筛选</span><br><span class="line"></span><br><span class="line">-- having: 分组的时候，在分组后用having代替where来对分组后的数据进行筛选</span><br><span class="line">-- 获取平均分数大于60分的学生的id</span><br><span class="line">SELECT stuid,avg(mark) FROM tb_score GROUP BY(stuid) HAVING avg(mark)>60;</span><br><span class="line"></span><br><span class="line">-- 3.子查询: 将一个查询操作的结果作为另外一个查询的数据源</span><br><span class="line">-- 在tb_score表中获取成绩是大于90分的学生的id</span><br><span class="line">SELECT stuid FROM tb_score WHERE mark>90 and stuid is not NULL; </span><br><span class="line"></span><br><span class="line">-- 获取成绩大于90分的学生的名字</span><br><span class="line">SELECT stuname FROM tb_student WHERE stuid in </span><br><span class="line">(SELECT stuid FROM tb_score WHERE mark>90 and stuid is not NULL); </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">SELECT stuid,mark FROM tb_score WHERE mark > 90 and stuid is not NULL;</span><br><span class="line">-- 将一个查询的结果作为查询对象提供给另外一个查询。但是第一个查询结果需要重命名</span><br><span class="line">SELECT mark FROM (SELECT stuid,mark FROM tb_score WHERE mark > 90 and stuid is not NULL) as t2;</span><br><span class="line"></span><br><span class="line">-- ========================连接查询===============================</span><br><span class="line">-- 1.连接查询：同时查询多个表中的数据</span><br><span class="line">-- select * from 表名1,表名2... where 连接条件;</span><br><span class="line">-- 连接查询如果不加连接条件，结果是笛卡尔积：(a,b,c)(1,2,3)——>(a1,a2,a3,b1,b2,b3,c1,c2,c3)</span><br><span class="line"></span><br><span class="line">-- 获取老师姓名和其对应的学院名</span><br><span class="line">select teaname,collname from tb_college,tb_teaher where tb_college.collid=tb_student.collid;</span><br><span class="line"></span><br><span class="line">-- 获取学生姓名和其指定课程的分数</span><br><span class="line">select stuname,couname,mark from tb_student,tb_course,tb_score where tb_student.stuid=tb_score.stuid and tb_course.couid=tb_score.couid;</span><br><span class="line"></span><br><span class="line">-- 注意：如果连接查询的时候既有连接条件又有筛选条件，我们要把筛选条件写在连接条件后面</span><br><span class="line">-- 查询平均成绩大于80分的学生姓名对应的学生的平均成绩</span><br><span class="line">select stuname,avg_mark from tb_student,(select stuid,avg(mark) as avg_mark from tb_score group by(stuid)) as temp_t where tb_student.stuid = temp_t.stuid and avg_mark>80;</span><br><span class="line"></span><br><span class="line">-- 2.内连接</span><br><span class="line">-- select * from 表1 inner join 表2 on 表2的连接条件 inner join 表3 on 表3的连接条件 ...;</span><br><span class="line">-- 注意：中间表写在最前面（存在关联其他表外键的表）</span><br><span class="line">-- 查询学生姓名对应的学科名的分数</span><br><span class="line">select stuname,couname,mark from tb_score inner join tb_student on tb_student.stuid=tb_score.stuid inner join tb_course on tb_course.couid=tb_score.couid where mark<60;</span><br><span class="line">-- 内连接把满足条件的记录取出来</span><br><span class="line">-- 3.外连接</span><br><span class="line">-- 外连接分为左外连接、右外连接和全连接，但是在mysql中只支持左外连接和右外连接</span><br><span class="line">-- 表1(左表) left/right/inner jion 表2(右表)</span><br><span class="line">-- 左外连接：将左表中所有对应字段的所有数据取出，然后再查出对应的右表中对应字段的值，如果右表对应的值不存在结果为null</span><br><span class="line">-- 右外连接：将右表中所有对应字段的所有数据取出，然后再查出对应的左表中对应字段的值，如果左表对应的值不存在结果为null</span><br><span class="line">-- 查所有学生名对应的成绩</span><br><span class="line">select stuname,mark from tb_score inner join tb_student on tb_student.stuid=tb_score.stuid;</span><br><span class="line">select stuname,mark from tb_score left join tb_student on tb_student.stuid=tb_score.stuid;</span><br><span class="line"></span><br><span class="line">-- ========================字段索引==============================</span><br><span class="line">-- explain: 获取执行</span><br><span class="line"></span><br><span class="line">-- 字段的索引就相当于目录，作用是为了能够快速的对这个字段进行查找</span><br><span class="line">-- 添加索引的好处是可以大大的提高查询效率； 缺点：1.会消耗额外的存储空间 2.会让添加和删除的效率降低。</span><br><span class="line">-- 建议：1. 索引不能滥用 2.如果项目中针对某个字段的查询很频繁，建议加个对应的索引</span><br><span class="line">explain select * from tb_student where stuid=1;</span><br><span class="line">explain select * from tb_student where stuname='张三';</span><br><span class="line"></span><br><span class="line">-- 添加索引</span><br><span class="line">-- create index 索引名称 on 表名 (字段名); - 给指定表中的指定字段添加索引</span><br><span class="line">create index index_stuname on tb_student (stuname); -- 给名字加索引</span><br><span class="line">create index index_stuname1 on tb_student (stuname(1)); -- 按姓加索引</span><br><span class="line"></span><br><span class="line">-- 删除索引</span><br><span class="line">alter table tb_student drop index index_stuname;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- =========================DCL========================</span><br><span class="line">-- 1.创建用户</span><br><span class="line">-- create user 用户名@登录地址</span><br><span class="line">-- 登录地址: (限制用户能够登录mysql的主机地址)，ip地址(指定地址)，localhost(数据库本机)，%(任何位置)</span><br><span class="line">create user 'zhangsan'@'%' identified by 'aaaaaa'; </span><br><span class="line">-- 删除用户: drop user 用户名;</span><br><span class="line">drop user 用户名;</span><br><span class="line"></span><br><span class="line">-- 2.授权</span><br><span class="line">-- grant 权限类型 on 数据库.对象 to 用户名;</span><br><span class="line">grant select on *.* to 'zhangshan';</span><br><span class="line">grant update on *.* to 'zhangshan';</span><br><span class="line">grant all privileges on *.* to 'zhangshan'; -- 添加所有权限</span><br><span class="line">grant all privileges on *.* to 'zhangshan' with grant option; -- 添加所有权限，并且能够将自己的权限再授权给其他用户</span><br><span class="line"></span><br><span class="line">-- 3.召回授权</span><br><span class="line">-- revoke 权限类型 on 数据库.对象 from 用户名;</span><br><span class="line">revoke delete on school.* from 'zhangshan';</span><br><span class="line"></span><br><span class="line">-- 4.事务</span><br><span class="line">-- 完成一个任务需要执行多条sql，但是要求这多个操作当中只要有一个操作失败，整个任务就失败，数据全部还原，所有的操作都成功整个任务才成功的时候就使用事务。</span><br><span class="line"></span><br><span class="line">-- 开启事务环境</span><br><span class="line">begin;</span><br><span class="line">update tb_student set stuname = '一一' where stuname='12';</span><br><span class="line">delete from tb_student where stuid=110;</span><br><span class="line"></span><br><span class="line">-- 提交事务(只有begin到commit之间的所有的sql都执行成功，才会执行commit；否则执行rollback)</span><br><span class="line">commit;</span><br><span class="line"></span><br><span class="line">-- 事务回滚(放弃begin到commit之间执行成功的所有sql语句的结果)</span><br><span class="line">rollback;</span><br><span class="line"></span><br><span class="line">-- 8.pyMySQL</span><br><span class="line">1.建立连接</span><br><span class="line"> host - 要连接的数据库所在的主机地址(远程连接用ip地址，本机使用'localhost')</span><br><span class="line"> user - 用户名</span><br><span class="line"> password - 密码</span><br><span class="line"> database - 数据库</span><br><span class="line"> port - 端口</span><br><span class="line"> charset - 编码方式</span><br><span class="line"> con_obj = pymysql.connect(host='47.101.0.09',</span><br><span class="line"> user='root',</span><br><span class="line"> password='aaaaa',</span><br><span class="line"> database='school',</span><br><span class="line"> port=3306,</span><br><span class="line"> charset='utf8',</span><br><span class="line"> autocommit=True</span><br><span class="line"> )</span><br><span class="line"> print(con_obj)</span><br><span class="line"></span><br><span class="line"> 2.获得游标对象 - 提供数据库操作的上下文</span><br><span class="line"> 注意：游标提供的上下文是事务环境</span><br><span class="line"> with con_obj.cursor() as cursor:</span><br><span class="line"> 在这后面操作数据库</span><br><span class="line"> 3.操作数据库，执行sql语句：连接对象.execute(sql语句)</span><br><span class="line"> 返回执行结果，如果是增删改操作，结果是否成功：1-成功，0-失败</span><br><span class="line"> result = cursor.execute("update tb_teacher set teaage=25;")</span><br><span class="line"> print(result)</span><br><span class="line"></span><br><span class="line"> 事务提交</span><br><span class="line"> con_obj.commit()</span><br><span class="line"></span><br><span class="line"> 关闭连接：连接对象.close()</span><br><span class="line"> con_obj.close()</span><br></pre></td></tr></table></figure>
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<time title="创建时间：2019-02-25 20:26:51 / 修改时间：20:26:44" itemprop="dateCreated datePublished" datetime="2019-02-25T20:26:51+08:00">2019-02-25</time>
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