MongoDB—SQL到MongoDB映射图表

一、术语和概念

下表显示了各种 SQL 术语和概念 以及相应的 MongoDB 术语和概念。

SQL Terms/Concepts	MongoDB Terms/Concepts
database	database
table	collection
row	document or BSON document
column	field
index	index
table joins	$lookup, embedded documents
primary key Specify any unique column or column combination as primary key.	primary key In MongoDB, the primary key is automatically set to the _id field.
aggregation (e.g. group by)	aggregation pipeline See the SQL to Aggregation Mapping Chart.
SELECT INTO NEW_TABLE	$out See the SQL to Aggregation Mapping Chart.
MERGE INTO TABLE	$merge (Available starting in MongoDB 4.2) See the SQL to Aggregation Mapping Chart.
UNION ALL	$unionWith (Available starting in MongoDB 4.4)
transactions	transactions

二、可执行程序

下表显示了一些数据库可执行文件和相应的MongoDB可执行文件。本表并非详尽无遗。

三、示例

下表显示了各种SQL语句和相应的MongoDB语句。表中的示例假设以下条件：

• SQL示例假设一个名为people的表。
• MongoDB示例假设一个名为people的集合包含以下原型的文档： 

{
  _id: ObjectId("509a8fb2f3f4948bd2f983a0"),
  user_id: "abc123",
  age: 55,
  status: 'A'
}

 1、Create and Alter

下表显示了与表级操作相关的各种SQL语句以及相应的MongoDB语句。

SQL Schema Statements	MongoDB Schema Statements
CREATE TABLE people ( id MEDIUMINT NOT NULL AUTO_INCREMENT, user_id Varchar(30), age Number, status char(1), PRIMARY KEY (id) )	​ 在第一个insertOne（）或insertMany（）操作上隐式创建。如果未指定_id字段，则自动添加主键_id。 ​ db.people.insertOne( { user_id: "abc123", age: 55, status: "A" } ) 然而，您也可以显式创建集合： db.createCollection("people")
ALTER TABLE people ADD join_date DATETIME	​托收不描述或强制执行其文件的结构；即，在收集级别没有结构变化。 然而，在文档级别，updateMany（）操作可以使用$set操作符将字段添加到现有文档中。 db.people.updateMany( { }, { $set: { join_date: new Date() } } )
ALTER TABLE people DROP COLUMN join_date	​托收不描述或强制执行其文件的结构；即，在收集级别没有结构变化。 然而，在文档级别，updateMany（）操作可以使用$unset操作符从文档中删除字段。​ db.people.updateMany( { }, { $unset: { "join_date": "" } } )
CREATE INDEX idx_user_id_asc ON people(user_id)	db.people.createIndex( { user_id: 1 } )
CREATE INDEX idx_user_id_asc_age_desc ON people(user_id, age DESC)	db.people.createIndex( { user_id: 1, age: -1 } )
DROP TABLE people	db.people.drop()

 2、Insert

下表显示了与将记录插入表中相关的各种SQL语句以及相应的MongoDB语句。

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

3、select

 下表显示了与从表中读取记录相关的各种SQL语句以及相应的MongoDB语句。

SQL SELECT Statements	MongoDB find() Statements
SELECT * FROM people	db.people.find()
SELECT id, user_id, status FROM people	db.people.find( { }, { user_id: 1, status: 1 } )
SELECT user_id, status FROM people	db.people.find( { }, { user_id: 1, status: 1, _id: 0 } )
SELECT * FROM people WHERE status = "A"	db.people.find( { status: "A" } )
SELECT user_id, status FROM people WHERE status = "A"	db.people.find( { status: "A" }, { user_id: 1, status: 1, _id: 0 } )
SELECT * FROM people WHERE status != "A"	db.people.find( { status: { $ne: "A" } } )
SELECT * FROM people WHERE status = "A" AND age = 50	db.people.find( { status: "A", age: 50 } )
SELECT * FROM people WHERE status = "A" OR age = 50	db.people.find( { $or: [ { status: "A" } , { age: 50 } ] } )
SELECT * FROM people WHERE age > 25	db.people.find( { age: { $gt: 25 } } )
SELECT * FROM people WHERE age < 25	db.people.find( { age: { $lt: 25 } } )
SELECT * FROM people WHERE age > 25 AND age <= 50	db.people.find( { age: { $gt: 25, $lte: 50 } } )
SELECT * FROM people WHERE user_id like "%bc%"	db.people.find( { user_id: /bc/ } ) -or- db.people.find( { user_id: { $regex: /bc/ } } )
SELECT * FROM people WHERE user_id like "bc%"	db.people.find( { user_id: /^bc/ } ) -or- db.people.find( { user_id: { $regex: /^bc/ } } )
SELECT * FROM people WHERE status = "A" ORDER BY user_id ASC	db.people.find( { status: "A" } ).sort( { user_id: 1 } )
SELECT * FROM people WHERE status = "A" ORDER BY user_id DESC	db.people.find( { status: "A" } ).sort( { user_id: -1 } )
SELECT COUNT(*) FROM people	db.people.count() or db.people.find().count()
SELECT COUNT(user_id) FROM people	db.people.count( { user_id: { $exists: true } } ) or db.people.find( { user_id: { $exists: true } } ).count()
SELECT COUNT(*) FROM people WHERE age > 30	db.people.count( { age: { $gt: 30 } } ) or db.people.find( { age: { $gt: 30 } } ).count()
SELECT DISTINCT(status) FROM people	db.people.aggregate( [ { $group : { _id : "$status" } } ] ) ​或者，对于不超过BSON大小限制的不同值集 db.people.distinct( "status" )
SELECT * FROM people LIMIT 1	db.people.findOne() or db.people.find().limit(1)
SELECT * FROM people LIMIT 5 SKIP 10	db.people.find().limit(5).skip(10)
EXPLAIN SELECT * FROM people WHERE status = "A"	db.people.find( { status: "A" } ).explain()

4、update

下表显示了与更新表中现有记录相关的各种SQL语句以及相应的MongoDB语句。 

SQL Update Statements	MongoDB updateMany() Statements
UPDATE people SET status = "C" WHERE age > 25	db.people.updateMany( { age: { $gt: 25 } }, { $set: { status: "C" } } )
UPDATE people SET age = age + 3 WHERE status = "A"	db.people.updateMany( { status: "A" } , { $inc: { age: 3 } } )