强强对比 MongoDB与MySQL

Posted 2021-05-01 K8S中文社区

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作者: MoonlightL

原标题：MongoDB 与 mysql 的区别 / 原文:

https://www.extlight.com/2017/11/30/MongoDB-与-MySQL-的区别/

一、前言

MongoDB 虽说是文档型数据库，但是在学习和使用其语法时发现又与 MySQL 有些相似之处，在此记录点滴日后复习。

二、概念区别

比较	MySQL	MongoDB
库	database	database
表	table	collection
行	row	document
列	column	field
索引	index	index
表关联	table joins	$lookup
主键	primary key	primary key
聚合	aggregation	aggregation pipeline

三、命令区别

比较	MySQL	MongoDB
服务端	mysqld	mongod
客户端	mysql	mongo

四、关键字和函数区别

MySQL	MongoDB
where	$match
group by	$group
having	$match
select	$project
order by	$sort
limit	$limit
sum()	$sum
count()	$sum
join	$lookup

五、语句区别

# 5.1 表结构

# 5.1.1 创建表/集合


  
    
    
   
   db.people.insertOne( {
 
   user_id: "abc123",
 
   age: 55,
 
   status: "A"
 
   } )
 
   
 
   相当于
 
   
 
   CREATE TABLE people (
 
   id MEDIUMINT NOT NULL AUTO_INCREMENT,
 
   user_id Varchar(30),
 
   age Number,
 
   status char(1),
 
   PRIMARY KEY (id)
 
   )

# 5.1.2 新增字段


  
    
    
   
   db.people.updateMany(
 
   { },
 
   { $set: { join_date: new Date() } }
 
   )
 
   
 
   相当于 ALTER TABLE people ADD join_date DATETIME

# 5.1.3 删除字段


  
    
    
   
   db.people.updateMany(
 
   { },
 
   { $unset: { "join_date": "" } }
 
   )
 
   
 
   相当于 ALTER TABLE people DROP COLUMN join_date

# 5.1.4 创建索引


  
    
    
   
   db.people.createIndex( { user_id: 1 } )
 
   
 
   相当于 CREATE INDEX idx_user_id_asc ON people(user_id)

# 5.1.5 删除表/集合


  
    
    
   
   db.people.drop()
 
   
 
   相当于 DROP TABLE people

# 5.2 新增记录/文档


  
    
    
   
   db.people.insertOne(
 
   { user_id: "bcd001", age: 45, status: "A" }
 
   )
 
   
 
   相当于 INSERT INTO people(user_id,age,status) VALUES ("bcd001",45,"A")

# 5.3 查询记录/文档

# 5.3.1 简单查询


  
    
    
   
   db.people.find()
 
   
 
   相当于 SELECT * FROM people


  
    
    
   
   db.people.find(
 
   { },
 
   { user_id: 1, status: 1 }
 
   )
 
   
 
   相当于 SELECT id,user_id,status FROM people


  
    
    
   
   db.people.find(
 
   { },
 
   { user_id: 1, status: 1, _id: 0 }
 
   )
 
   
 
   相当于 SELECT user_id, status FROM people

# 5.3.2 条件查询


  
    
    
   
   db.people.find(
 
   { status: "A" }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE status = "A"


  
    
    
   
   db.people.find(
 
   { status: "A" },
 
   { user_id: 1, status: 1, _id: 0 }
 
   )
 
   
 
   相当于 SELECT user_id, status FROM people WHERE status = "A"

# 5.3.3 非查询


  
    
    
   
   db.people.find(
 
   { status: { $ne: "A" } }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE status != "A"

# 5.3.4 且查询


  
    
    
   
   db.people.find(
 
   { status: "A",
 
   age: 50 }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE status = "A" AND age = 50

# 5.3.5 或查询


  
    
    
   
   db.people.find(
 
   { $or: [ { status: "A" } ,
 
   { age: 50 } ] }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE status = "A" OR age = 50

# 5.3.6 大于查询


  
    
    
   
   db.people.find(
 
   { age: { $gt: 25 } }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE age > 25

# 5.3.7 小于查询


  
    
    
   
   db.people.find(
 
   { age: { $lt: 25 } }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE age < 25

# 5.3.8 范围查询


  
    
    
   
   db.people.find(
 
   { age: { $gt: 25, $lte: 50 } }
 
   )
 
   
 
   相当于 SELECT * FROM people WHERE age > 25 AND age <= 50

# 5.3.9 模糊查询


  
    
    
   
   db.people.find( { user_id: /bc/ } ) 或 db.people.find( { user_id: { $regex: /bc/ } } )
 
   
 
   相当于 SELECT * FROM people WHERE user_id like "%bc%"


  
    
    
   
   db.people.find( { user_id: /^bc/ } ) 或 db.people.find( { user_id: { $regex: /^bc/ } } )
 
   
 
   相当于 SELECT * FROM people WHERE user_id like "bc%"

# 5.3.10 排序查询


  
    
    
   
   db.people.find( { status: "A" } ).sort( { user_id: 1 } )
 
   
 
   相当于 SELECT * FROM people WHERE status = "A" ORDER BY user_id ASC


  
    
    
   
   db.people.find( { status: "A" } ).sort( { user_id: -1 } )
 
   
 
   相当于 SELECT * FROM people WHERE status = "A" ORDER BY user_id DESC

# 5.3.11 统计查询


  
    
    
   
   db.people.count() 或 db.people.find().count()
 
   
 
   相当于 SELECT COUNT(*) FROM people


  
    
    
   
   db.people.count( { user_id: { $exists: true } } ) 或 db.people.find( { user_id: { $exists: true } } ).count()
 
   
 
   相当于 SELECT COUNT(user_id) FROM people


  
    
    
   
   db.people.count( { age: { $gt: 30 } } ) 或 db.people.find( { age: { $gt: 30 } } ).count()
 
   
 
   相当于 SELECT COUNT(*) FROM people WHERE age > 30

# 5.3.12 去重查询


  
    
    
   
   db.people.distinct( "status" )
 
   
 
   相当于 SELECT DISTINCT(status) FROM people

# 5.3.13 分页查询


  
    
    
   
   db.people.findOne() 或 db.people.find().limit(1)
 
   
 
   相当于 SELECT * FROM people LIMIT 1


  
    
    
   
   db.people.find().limit(5).skip(10)
 
   
 
   相当于 SELECT * FROM people LIMIT 5 SKIP 10

# 5.3.14 查询计划


  
    
    
   
   db.people.find( { status: "A" } ).explain()
 
   
 
   相当于 EXPLAIN SELECT * FROM people WHERE status = "A"

# 5.4 修改记录/文档


  
    
    
   
   db.people.updateMany(
 
   { age: { $gt: 25 } },
 
   { $set: { status: "C" } }
 
   );
 
   
 
   相当于 UPDATE people SET status = "C" WHERE age > 25;
 
   
 
   db.people.updateMany(
 
   { status: "A" } ,
 
   { $inc: { age: 3 } }
 
   );
 
   
 
   相当于 UPDATE people SET age = age + 3 WHERE status = "A";

# 5.5 删除记录/文档


  
    
    
   
   db.people.deleteMany( { status: "D" } );
 
   
 
   相当于 DELETE FROM people WHERE status = "D";
 
   
 
   db.people.deleteMany({});
 
   
 
   相当于 DELETE FROM people;

六、参考资料

https://docs.mongodb.com/manual/reference/sql-aggregation-comparison/ 关键字和函数相关
https://docs.mongodb.com/manual/reference/sql-comparison/ 语句相关