mongo语法和mysql语法对比学习

缺乏、安全感 2022-05-20 07:48 143阅读 0赞

转自：[https://blog.csdn.net/lovesummerforever/article/details/40147607][https_blog.csdn.net_lovesummerforever_article_details_40147607]

mongodb全套学习：[https://blog.csdn.net/lovesummerforever/article/category/2632581][https_blog.csdn.net_lovesummerforever_article_category_2632581]

#### 总结： ####

mongodb语法很多，比如多列索引，查询时可以统计函数，支持多条件查询，但是目前对多表的查询是不支持的，可以想办法通过数据冗余来解决多表查询的问题。

原文提到一个查询指定字段的用法，但是没有详细说一下，自己作记录：

来自：[https://www.cnblogs.com/leskang/p/6000852.html][https_www.cnblogs.com_leskang_p_6000852.html]

db.collection1.find(\{age:7\},\{name:1\});//select name from collection1 where age=7;  
//查询年龄为7的数据，只返回name字段数据；**两个大括号，前面的存查询条件，后面的存返回条件，返回条件字段1表示true，表示此字段返回，如果name后面的1改为0则表示不返回name字段，返回除name字段以外的其他字段  
注意：如果设置返回字段有为0的已经表示查询所有除了某字段以外的所有字段就不能再设置某个字段为1了，有语法冲突**

db.collection1.find(\{age:7,name:"xiaomu"\},\{name:1,age:1\});

//select name,age from collection1 where age=7 and name="xiaomu"

//查询age为7，name为xiaomu的数据，返回name和age字段注：多条件查询此处是并列，**但是如果多个条件都相同的话如\{name:"xiaoli",name:"xioamu"\}则会只查询后一个条件的数据**

#### **原文：** ####

我们总是在对比中看到自己的优点和缺点，对于mongodb来说也是一样，对比学习让我们尽快的掌握关于mongodb的基础知识。

mongodb与mysql命令对比

关系型数据库一般是由数据库（database）、表（table）、记录（record）三个层次概念组成。而非关系型数据库mongodb是由数据库（database）、集合（collection）、文档对象（document）三个层次组成。mongodb对于关系型数据库里的表，没有行和列的关系概念，这体现了模式的自由特点。

语法命令如下列表格所示

<table style="border-spacing:0px;border-style:solid;border-color:rgb(163,163,163);border-width:1pt;"> 
 <tbody> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">MySQL</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">MongoDB</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">说明</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">mysqld</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongod</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">服务器守护进程</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">mysql</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongo</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">客户端工具</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">mysqldump</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongodump</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">逻辑备份工具</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">mysql</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongorestore</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">逻辑恢复工具</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.repairDatabase()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">修复数据库</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">mysqldump</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongoexport</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">数据导出工具</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">source</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">mongoimport</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">数据导入工具</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">grant * privileges on *.* to …</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">Db.addUser()Db.auth()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">新建用户并权限</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">show databases</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">show dbs</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">显示库列表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Show tables</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">Show collections</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">显示表列表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Show slave status</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">Rs.status</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查询主从状态</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Create table users(a int, b int)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.createCollection("mycoll", {capped:true,size:100000}) 另：可隐式创建表。</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">创建表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Create INDEX idxname ON users(name)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.ensureIndex({name:1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">创建索引</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Create INDEX idxname ON users(name,ts DESC)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.ensureIndex({name:1,ts:-1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">创建索引</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Insert into users values(1, 1)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.insert({a:1, b:1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">插入记录</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Select a, b from users</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({},{a:1, b:1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查询表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Select * from users</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查询表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Select * from users where age=33</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({age:33})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">Select a, b from users where age=33</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({age:33},{a:1, b:1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where age&lt;33</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({'age':{$lt:33}})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where age&gt;33 and age&lt;=40</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({'age':{$gt:33,$lte:40}})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where a=1 and b='q'</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({a:1,b:'q'})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where a=1 or b=2</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find( { $or : [ { a : 1 } , { b : 2 } ] } )</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users limit 1</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.findOne()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">条件查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where name like "%Joe%"</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({name:/Joe/})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">模糊查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users where name like "Joe%"</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({name:/^Joe/})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">模糊查询</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select count(1) from users</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">Db.users.count()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">获取表记录数</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select count(1) from users where age&gt;30</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({age: {'$gt': 30}}).count()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">获取表记录数</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select DISTINCT last_name from users</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.distinct('last_name')</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">去掉重复值</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users ORDER BY name</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find().sort({name:-1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">排序</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">select * from users ORDER BY name DESC</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find().sort({name:-1})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">排序</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">EXPLAIN select * from users where z=3</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.find({z:3}).explain()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">获取存储路径</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">update users set a=1 where b='q'</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.update({b:'q'}, {$set:{a:1}}, false, true)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">更新记录</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">update users set a=a+2 where b='q'</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.update({b:'q'}, {$inc:{a:2}}, false, true)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">更新记录</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">delete from users where z="abc"</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.remove({z:'abc'})</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">删除记录</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db. users.remove()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">删除所有的记录</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">drop database IF EXISTS test;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">use testdb.dropDatabase()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">删除数据库</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">drop table IF EXISTS test;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.mytable.drop()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">删除表/collection</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.addUser(‘test’, ’test’)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">添加用户readOnly--&gt;false</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.addUser(‘test’, ’test’, true)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">添加用户readOnly--&gt;true</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.addUser("test","test222")</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">更改密码</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.system.users.remove({user:"test"})或者db.removeUser('test')</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">删除用户</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">use admin</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">超级用户</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.auth(‘test’, ‘test’)</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">用户授权</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.system.users.find()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看用户列表</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">show users</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看所有用户</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.printCollectionStats()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看各collection的状态</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.printReplicationInfo()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看主从复制状态</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">show profile</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看profiling</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.copyDatabase('mail_addr','mail_addr_tmp')</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">拷贝数据库</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db.users.dataSize()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查看collection数据的大小</td> 
 </tr> 
 <tr> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8715in;">&nbsp;</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.7479in;">db. users.totalIndexSize()</td> 
 <td style="border-width:1pt;border-color:rgb(163,163,163);vertical-align:top;width:1.8756in;">查询索引的大小</td> 
 </tr> 
 </tbody> 
</table>

mongodb语法说明

mongodb语法很多，比如多列索引，查询时可以统计函数，支持多条件查询，但是目前对多表的查询是不支持的，可以想办法通过数据冗余来解决多表查询的问题。举例如下所示。

查询colls所有数据 
        db.colls.find() //select \* from colls  
    通过指定条件查询 
        db.colls.find(\{‘last\_name': ‘Smith'\});//select \* from colls where last\_name='Smith'  
    指定多条件查询 
        db.colls.find( \{ x : 3, y : “foo” \} );//select \* from colls where x=3 and y='foo' 
 
 
    指定条件范围查询 
        db.colls.find(\{j: \{$ne: 3\}, k: \{$gt: 10\} \});//select \* from colls where j!=3 and k>10 
 
 
    查询不包括某内容 
        db.colls.find(\{\}, \{a:0\});//查询除a为0外的所有数据 
 
 
    支持<, <=, >, >=查询，需用符号替代分别为$lt，$lte，$gt，$gte 
        db.colls.find(\{ “field” : \{ $gt: value \} \} );  
        db.colls.find(\{ “field” : \{ $lt: value \} \} );  
        db.colls.find(\{ “field” : \{ $gte: value \} \} ); 
        db.colls.find(\{ “field” : \{ $lte: value \} \} ); 
 
 
    也可对某一字段做范围查询 
        db.colls.find(\{ “field” : \{ $gt: value1, $lt: value2 \} \} ); 
 
 
    不等于查询用字符$ne 
        db.colls.find( \{ x : \{ $ne : 3 \} \} ); 
 
 
    in查询用字符$in 
        db.colls.find( \{ “field” : \{ $in : array \} \} ); 
        db.colls.find(\{j:\{$in: \[2,4,6\]\}\}); 
 
 
    not in查询用字符$nin 
        db.colls.find(\{j:\{$nin: \[2,4,6\]\}\}); 
 
 
    取模查询用字符$mod 
        db.colls.find( \{ a : \{ $mod : \[ 10 , 1 \] \} \} )// where a % 10 == 1 
 
 
    $all查询 
        db.colls.find( \{ a: \{ $all: \[ 2, 3 \] \} \} );//指定a满足数组中任意值时 
 
 
    $size查询 
        db.colls.find( \{ a : \{ $size: 1 \} \} );//对对象的数量查询，此查询查询a的子对象数目为1的记录 
 
 
    $exists查询 
        db.colls.find( \{ a : \{ $exists : true \} \} ); // 存在a对象的数据 
        db.colls.find( \{ a : \{ $exists : false \} \} ); // 不存在a对象的数据 
 
 
    $type查询$type值为bsonhttp://bsonspec.org/数 据的类型值 
        db.colls.find( \{ a : \{ $type : 2 \} \} ); // 匹配a为string类型数据 
        db.colls.find( \{ a : \{ $type : 16 \} \} ); // 匹配a为int类型数据 
 
 
    使用正则表达式匹配 
        db.colls.find( \{ name : /acme.\*corp/i \} );//类似于SQL中like 
 
 
    内嵌对象查询 
        db.colls.find( \{ “author.name” : “joe” \} ); 
 
 
    1.3.3版本及更高版本包含$not查询 
        db.colls.find( \{ name : \{ $not : /acme.\*corp/i \} \} ); 
        db.colls.find( \{ a : \{ $not : \{ $mod : \[ 10 , 1 \] \} \} \} ); 
 
 
    sort()排序 
        db.colls.find().sort( \{ ts : -1 \} );//1为升序2为降序 
 
 
    limit()对限制查询数据返回个数 
        db.colls.find().limit(10) 
 
 
    skip()跳过某些数据 
        db.colls.find().skip(10) 
 
 
    snapshot()快照保证没有重复数据返回或对象丢失 
 
 
    count()统计查询对象个数 
        db.students.find(\{‘address.state' : ‘CA'\}).count();//效率较高 
        db.students.find(\{‘address.state' : ‘CA'\}).toArray().length;//效率很低 
 
 
    group()对查询结果分组和SQL中group by函数类似 
    distinct()返回不重复值

[https_blog.csdn.net_lovesummerforever_article_details_40147607]: https://blog.csdn.net/lovesummerforever/article/details/40147607
[https_blog.csdn.net_lovesummerforever_article_category_2632581]: https://blog.csdn.net/lovesummerforever/article/category/2632581
[https_www.cnblogs.com_leskang_p_6000852.html]: https://www.cnblogs.com/leskang/p/6000852.html