# 函数
随机数 rand()
连接字符串 concat('中国','打日本')
转换小写 lcase('ABC') lower
转换大写 upper ucase
去除空格 trim(str)
```
<pre class="calibre14">```
<span class="token1">curdate</span><span class="token2">(</span><span class="token2">)</span><span class="token">+</span><span class="token3">0</span> 返回<span class="token3">20160916</span>
<span class="token1">curdate</span><span class="token2">(</span><span class="token2">)</span> <span class="token3">2016</span><span class="token">-</span><span class="token3">09</span><span class="token">-</span><span class="token3">16</span>
<span class="token1">curtime</span><span class="token2">(</span><span class="token2">)</span> <span class="token3">21</span><span class="token2">:</span><span class="token3">53</span><span class="token2">:</span><span class="token3">23</span>
<span class="token1">now</span><span class="token2">(</span><span class="token2">)</span> <span class="token3">2019</span><span class="token">-</span><span class="token3">07</span><span class="token">-</span><span class="token3">10</span> <span class="token3">21</span><span class="token2">:</span><span class="token3">52</span><span class="token2">:</span><span class="token3">23</span>日期时间
<span class="token1">unix_timestamp</span><span class="token2">(</span><span class="token1">now</span><span class="token2">(</span><span class="token2">)</span><span class="token2">)</span> 返回时间戳 <span class="token3">1562767275</span>
<span class="token1">from_unixtime</span><span class="token2">(</span> <span class="token3">1539659520</span><span class="token2">)</span> 返回 <span class="token3">2018</span><span class="token">-</span><span class="token3">10</span><span class="token">-</span><span class="token3">16</span> <span class="token3">11</span><span class="token2">:</span><span class="token3">12</span><span class="token2">:</span><span class="token3">00</span>
<span class="token1">from_unixtime</span><span class="token2">(</span><span class="token3">1515980716</span><span class="token2">,</span> <span class="token4">'%Y-%m-%d %H:%i:%S'</span><span class="token2">)</span> <span class="token3">2018</span><span class="token">-</span><span class="token3">01</span><span class="token">-</span><span class="token3">15</span> <span class="token3">09</span><span class="token2">:</span><span class="token3">45</span><span class="token2">:</span><span class="token3">16</span> 格式化时间
<span class="token1">date_format</span><span class="token2">(</span><span class="token1">now</span><span class="token2">(</span><span class="token2">)</span><span class="token2">,</span> <span class="token4">'%Y-%m-%d'</span><span class="token2">)</span> <span class="token3">2018</span><span class="token">-</span><span class="token3">01</span><span class="token">-</span><span class="token3">15</span>
<span class="token1">date</span><span class="token2">(</span> <span class="token1">now</span><span class="token2">(</span><span class="token2">)</span><span class="token2">)</span> <span class="token3">2019</span><span class="token">-</span><span class="token3">07</span><span class="token">-</span><span class="token3">10</span> 提取日期
<span class="token1">year</span><span class="token2">(</span><span class="token4">'2019-7-10'</span><span class="token2">)</span> 返回<span class="token3">2019</span>
<span class="token1">month</span><span class="token2">(</span><span class="token4">'2016-04-28'</span><span class="token2">)</span> <span class="token3">4</span>
<span class="token1">day</span><span class="token2">(</span><span class="token1">now</span><span class="token2">(</span><span class="token2">)</span><span class="token2">)</span> <span class="token3">11</span> 返回天
<span class="token1">hour</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">)</span> <span class="token3">14</span>
<span class="token1">minute</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">)</span> <span class="token3">7</span>
<span class="token1">second</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">)</span> <span class="token3">50</span>
<span class="token1">last_day</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">)</span> <span class="token3">2019</span><span class="token">-</span><span class="token3">12</span><span class="token">-</span><span class="token3">31</span> 给定日期最后一天
<span class="token1">quarter</span><span class="token2">(</span><span class="token4">'2016-04-28'</span><span class="token2">)</span> <span class="token3">2</span> 季度<span class="token2">,</span><span class="token3">1</span><span class="token2">,</span><span class="token3">2</span><span class="token2">,</span><span class="token3">3</span><span class="token2">,</span><span class="token3">4</span>
<span class="token1">dayofweek</span><span class="token2">(</span><span class="token4">'2019-7-10'</span><span class="token2">)</span> 返回<span class="token3">4</span> 星期三 <span class="token">-</span><span class="token3">1</span>
<span class="token1">weekday</span><span class="token2">(</span><span class="token4">'2019-7-10'</span><span class="token2">)</span> 返回<span class="token3">2</span> 星期三<span class="token">+</span><span class="token3">1</span>
<span class="token1">dayofyear</span><span class="token2">(</span><span class="token4">'2019-7-10'</span><span class="token2">)</span> 返回今天是<span class="token3">191</span>天
<span class="token1">to_days</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">)</span> <span class="token3">737764</span>计算日期 d 距离 <span class="token3">0000</span> 年 <span class="token3">1</span> 月 <span class="token3">1</span> 日的天数
<span class="token1">from_days</span><span class="token2">(</span><span class="token3">733627</span><span class="token2">)</span> <span class="token3">2008</span><span class="token">-</span><span class="token3">08</span><span class="token">-</span><span class="token3">08</span> 同上相反
<span class="token1">day</span><span class="token2">(</span><span class="token1">last_day</span><span class="token2">(</span><span class="token1">now</span><span class="token2">(</span><span class="token2">)</span><span class="token2">)</span><span class="token2">)</span> 返回本月天数
<span class="token1">date_add</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">,</span>INTERVAL <span class="token3">1</span> day<span class="token2">)</span> <span class="token">+</span><span class="token3">1</span>天
<span class="token1">date_sub</span><span class="token2">(</span><span class="token4">'2019-12-6 14:7:50'</span><span class="token2">,</span>INTERVAL <span class="token3">1</span> day<span class="token2">)</span> <span class="token">-</span><span class="token3">1</span>天
<span class="token1">timestamp</span><span class="token2">(</span><span class="token4">'2008-08-08'</span><span class="token2">)</span> <span class="token3">2008</span><span class="token">-</span><span class="token3">08</span><span class="token">-</span><span class="token3">08</span> <span class="token3">00</span><span class="token2">:</span><span class="token3">00</span><span class="token2">:</span><span class="token3">00</span>
```
```
版本version
聚合函数
avg(col) 平均值
count(\*) 记录数
min(col) max(col)最小 最大值
sum(col)求和
- 简介
- 第一章 数据库
- Mysql/mariadb
- 函数
- 基础
- 增删改索引
- 标准查询
- 高级查询
- TIDB集群mysql解决方案
- Redis
- 语言基础
- 5种数据类型
- 其他类型
- Sqlite
- 语言基础
- 常用查询
- 第二章 PHP
- 语言基础
- 第一课 流程控制和运算
- 第二课 数组
- 第三课 日期时间
- 第四课 常用函数
- 第五课 字符串
- 第六课 文件操作
- 第七课 面向对象
- 第八课 正则表达式
- 第九课 图片处理生成
- 第十课 curl/memche
- 第十一课 mysql和pdo
- 第十三课 cookie和session
- 第十四课 xml操作
- 第十五课 php5.3+新特性
- 第十六课 php7+
- 第十七课 密码安全
- 废弃函数
- php命令行
- redis应用
- 算法
- 排序算法
- 基础算法
- 无限级分类
- 自定义函数Fn
- 查找算法
- 自定义函数数据函数fn
- laravel
- 路由
- 常用语句
- 数据库
- dingo/api
- Yii2
- 控制器
- 常用类
- 数据库
- redis
- thinkphp6
- TP6文档
- TP6插件
- dedecms
- 织梦标签大全
- 数据库操作
- 内置函数和定义函数
- 织梦核心改动
- 织梦插件/底层标签开发
- PHP相关工具
- composer
- php开发环境phpenv
- Phpstorm使用
- windows编译php扩展
- PHP开源库
- 开源项目管理禅道
- sns_auth
- php-casbin权限控制
- php-jwt
- 微信SDKeasywechat
- querylist采集库
- workerman
- Box/Spout处理excel和csv
- dll扩展
- redis/memche/xdebug
- redis
- Lua
- php_xlswriter
- event
- swoole
- 常用代码库
- 微擎框架
- 第一课全局变量
- 第二课常用函数
- 第三课自定义微擎独有函数
- 第四课数据库操作
- 第五课微信端回复
- 第六课微擎高级操作
- 第八课global函数列表
- mainfest.xml详解
- js方法
- 人人商城
- 第一课model解读
- 第二课常用语句解读
- 第三课常用js解读
- 第四课附录常见问题
- 第五课附录处理报表|支付
- 常用JSON状态码
- 第三章 JavaScript
- js基础
- 浏览器对象
- 语言基础
- html5接口
- ES6新语法
- vue
- 基础语法
- 京东vueUI组件
- uniapp
- 组件开发规范
- nodejs
- 基础知识
- 安装node
- nvm不同版本node切换
- js常用标准库
- zepto/jquery
- weui
- js图标库
- elementUI
- validator表单验证
- layer弹出层
- requirejs
- wow动画
- 动画animate
- swiper4
- 百度编辑器
- flyio/axios/qs
- jquery.form
- bootstrap3
- clipboard复制
- slideout侧滑
- imagehover.css图片悬停动画
- webpack打包
- Bulma UI框架
- store 客户端存储
- lottie动画创建库
- sweetalert
- js自定义函数
- 常见JSSDK
- 微信公众号JSSDK
- 腾讯地图jssdk
- 微信小程序
- 第四章 编程语言
- markdown语言
- Dart语言
- Dart语言基础
- Flutter框架
- Lua语言
- 字符串,数组,表
- 自定义方法
- go语言
- 第1.1语言基本语法
- 第1.2流程控制
- 第1.3函数
- 第1.4结构体
- 第1.5接口
- 第1.6包
- go语言框架Gin
- CSS3语言
- CSS与CSS3
- 选择符
- 属性
- css3
- loading动画
- HTML5语言
- less
- sass
- C#
- 基础知识
- 函数
- 第五章 开发工具
- git
- nginx/apache服务器
- Linux常用操作
- crontab定时任务
- 注册表与cmd
- 阿里云ECS
- frp穿透和ssl续期
- 宝塔安装
- 树莓派
- 浏览器模拟
- 火狐/chrome常用插件
- WSL安装使用
- mac brew和终端命令
- win10相关