MongoDB增删改查与传统型数据库的比较

传统型数据库的缺点：

1、数据结构要求高，必须遵循三大范式

2、存在join这样的多表查询，使得数据库在扩展方面很艰难

3、企业级数据库的license价格贵，并且随着系统的规模，不断上升

MongoDB的优势，面向集合存储、动态查询、文件存储格式为Bson、完全索引

MySQL	MongoDB
Table	Collection
Row	Document
Column	Field
Joins	Embedded documents, linking

MySQL	MongoDB
INSERT INTO users (user_id, age, status) VALUES ('bcd001', 45, 'A')	db.users.insert({   user_id: 'bcd001',   age: 45,   status: 'A' })
SELECT * FROM users	db.users.find()
UPDATE users SET status = 'C' WHERE age > 25	db.users.update(   { age: { $gt: 25 } },   { $set: { status: 'C' } },   { multi: true } )

增删改查：

增 insert :

insertOne

insertMany

删除：

remove/deleteOne/deleteMany

https://docs.mongodb.com/manual/reference/delete-methods/#additional-deletes

drop

https://docs.mongodb.com/manual/reference/method/db.collection.drop/

dropDatabase

https://docs.mongodb.com/manual/reference/method/db.dropDatabase/

改 update：

 

 查 find：

查询条件	MongoDB	MySQL
$and	db.inventory.find( { status: "A", qty: { $lt: 30 } } )	SELECT * FROM inventory WHERE status = "A" AND qty < 30
$in	db.inventory.find( { status: { $in: [ "A", "D" ] } } )	SELECT * FROM inventory WHERE status in ("A", "D")
$lt	db.inventory.find( { status: "A", qty: { $lt: 30 } } )	SELECT * FROM inventory WHERE status = "A" AND qty < 30
$or	db.inventory.find( { $or: [ { status: "A" }, { qty: { $lt: 30 } } ] } )	SELECT * FROM inventory WHERE status = "A" OR qty < 30
and & or	db.inventory.find( { status: "A", $or: [ { qty: { $lt: 30 } }, { item: /^p/ } ] } )	SELECT * FROM inventory WHERE status = "A" AND ( qty < 30 OR item LIKE "p%")

子查询：

 数组查询：

 

 普通查询：