Mongodb从0到1系列二：数据库与集合操作、文档增删改查
Mongodb从0到1系列一：下载、安装、启动、停止
3. 数据库与集合操作
数据库与集合的创建、查看、删除操作在mongodb server启动之后，打开一个mongo shell.
3.1 查看数据库
使用'show dbs'查看数据库：db2a:~ # mongo
MongoDB shell version v3.4.6
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.4.6
..
MongoDB Enterprise > show dbs
admin 0.000GB
local 0.000GB
3.2 创建/切换数据库
使用'use'创建/切换数据库：MongoDB Enterprise > use test1
switched to db test1
3.3 创建集合
集合类似于关系数据库中的表，使用db.createCollection(name，options) 方法创建集合student, teacherMongoDB Enterprise > db.createCollection("teacher")
{ "ok" : 1 }
MongoDB Enterprise > db.createCollection("student")
{ "ok" : 1 }
3.4 查看集合
使用'show collections'查看数据库中的集合：MongoDB Enterprise > show collections
student
teacher
3.4 删除集合
使用'db.COLLECTION_NAME.drop()'删除集合，其中COLLECTION_NAME表示集合名：
MongoDB Enterprise > db.student.drop()
true
MongoDB Enterprise > show collections
teacher
3.5 删除数据库
使用'db.dropDatabase()'命令删除当前数据库MongoDB Enterprise > show dbs
admin 0.000GB
local 0.000GB
test1 0.000GB
MongoDB Enterprise > db.dropDatabase()
{ "dropped" : "test1", "ok" : 1 }
MongoDB Enterprise > show dbs
admin 0.000GB
local 0.000GB
4. 文档增删改查
文档类似于关系数据库中的行， 集合其实是指文档的集合，集合创建完成之后，就可以在集合中增、删、改、查文档了：4.1 增加/插入文档
往teacher里插入三条文档。如果集合不存在的情况下，直接插入文档，那么会自动创建该集合，命令不必在一行完成：MongoDB Enterprise > use test1
switched to db test1
MongoDB Enterprise > db.createCollection("teacher")
{ "ok" : 1 }
MongoDB Enterprise > db.teacher.insert({name:'Wang',class:10,course:'math'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.teacher.insert({name:'Li',age:36,location:'Beijing',course:'English'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.teacher.insert({
... Firstname:'Miao',
... department:'GTS'
... })
WriteResult({ "nInserted" : 1 })
可以看到，同一个集合中的文档的结构并不要求一致，只要是键值对即可
4.2 查询文档
可以使用find()方法返回集合中的文档,加上pretty()的结果更加易读：MongoDB Enterprise > db.teacher.find()
{ "_id" : ObjectId("596ef911e1bc0d5b8e646a65"), "name" : "Wang", "class" : 10, "course" : "math" }
{ "_id" : ObjectId("596ef915e1bc0d5b8e646a66"), "name" : "Li", "age" : 36, "location" : "Beijing", "course" : "English" }
{ "_id" : ObjectId("596ef91fe1bc0d5b8e646a67"), "Firstname" : "Miao", "department" : "GTS" }{
"_id" : ObjectId("596ef911e1bc0d5b8e646a65"),
"name" : "Wang",
"class" : 10,
"course" : "math"
}
{
"_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
"name" : "Li",
"age" : 36,
"location" : "Beijing",
"course" : "English"
}
{
"_id" : ObjectId("596ef91fe1bc0d5b8e646a67"),
"Firstname" : "Miao",
"department" : "GTS"
}4.3 修改文档
有两个方法，一个是update()，主要用来更新；另一个是save()，主要用来替换已有文档修改1：将teacher中,将name为"Li"的文档的course修改为math:
MongoDB Enterprise > db.teacher.update({'name':'Li'},{$set:{'course':'math'}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
MongoDB Enterprise > db.teacher.find().pretty()
{
"_id" : ObjectId("596ef911e1bc0d5b8e646a65"),
"name" : "Wang",
"class" : 10,
"course" : "math"
}
{
"_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
"name" : "Li",
"age" : 36,
"location" : "Beijing",
"course" : "math"
}
{
"_id" : ObjectId("596ef91fe1bc0d5b8e646a67"),
"Firstname" : "Miao",
"department" : "GTS"
}修改2：上面的命令只修改第一条找到的记录，如果要修改所有满足条件的记录，可以加上{multi:true}，例如，要把所有course为math的文档的name修改为'Zhao'
MongoDB Enterprise > db.teacher.update({'course':'math'},{$set:{'name':'Zhao'}},{multi:true})
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })
MongoDB Enterprise > db.teacher.find().pretty()
{
"_id" : ObjectId("596ef911e1bc0d5b8e646a65"),
"name" : "Zhao",
"class" : 10,
"course" : "math"
}
{
"_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
"name" : "Zhao",
"age" : 36,
"location" : "Beijing",
"course" : "math"
}
{
"_id" : ObjectId("596ef91fe1bc0d5b8e646a67"),
"Firstname" : "Miao",
"department" : "GTS"
}修改3：将id为"596ef915e1bc0d5b8e646a66"的文档替换为如下：
{
"_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
"name" : "Li",
"age" : 36,
"location" : "Beijing",
"course" : "English",
"class" : 15,
"department": "computer"
}
这时候可以使用save()方法，执行以下命令：
MongoDB Enterprise > db.teacher.save({
... "_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
... "name" : "Li",
... "age" : 36,
... "location" : "Beijing",
... "course" : "English",
... "class" : 15,
... "department": "computer"
... }
... )
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
MongoDB Enterprise > db.teacher.find().pretty()
{
"_id" : ObjectId("596ef911e1bc0d5b8e646a65"),
"name" : "Zhao",
"class" : 10,
"course" : "math"
}
{
"_id" : ObjectId("596ef915e1bc0d5b8e646a66"),
"name" : "Li",
"age" : 36,
"location" : "Beijing",
"course" : "English",
"class" : 15,
"department" : "computer"
}
{
"_id" : ObjectId("596ef91fe1bc0d5b8e646a67"),
"Firstname" : "Miao",
"department" : "GTS"
}4.4 删除文档
先在student集合中插入几条记录:MongoDB Enterprise > db.student.insert({name:'miaoqingsong', course:'Computer'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.student.insert({name:'miaoqingsong', course:'English'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.student.insert({name:'Lilei', course:'Chinese'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.student.insert({name:'LiLei', course:'Chinese'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.student.insert({name:'LiLei', course:'Chinese'})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > db.student.find()
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a68"), "name" : "miaoqingsong", "course" : "Computer" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a69"), "name" : "miaoqingsong", "course" : "English" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6a"), "name" : "Lilei", "course" : "Chinese" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6b"), "name" : "LiLei", "course" : "Chinese" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6c"), "name" : "LiLei", "course" : "Chinese" }删除的格式如下：
db.collection.remove(
{
justOne:
writeConcern:
}
)
query :（可选）删除的文档的条件。
justOne : （可选）如果设为 true 或 1，则只删除一个文档。
writeConcern :（可选）抛出异常的级别。
删除1：删除所有name为miaoqingsong的文档:
MongoDB Enterprise > db.student.remove({name:'miaoqingsong'})
WriteResult({ "nRemoved" : 2 })
MongoDB Enterprise > db.student.find()
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6a"), "name" : "Lilei", "course" : "Chinese" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6b"), "name" : "LiLei", "course" : "Chinese" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6c"), "name" : "LiLei", "course" : "Chinese" }删除2：删除第一条course为Chinese的文档:
MongoDB Enterprise > db.student.remove({course:'Chinese'},{justOne:true})
WriteResult({ "nRemoved" : 1 })
MongoDB Enterprise > db.student.find()
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6b"), "name" : "LiLei", "course" : "Chinese" }
{ "_id" : ObjectId("596efa3ae1bc0d5b8e646a6c"), "name" : "LiLei", "course" : "Chinese" }删除3：删除所有的文档:
MongoDB Enterprise > db.student.remove({})
WriteResult({ "nRemoved" : 2 })
MongoDB Enterprise > db.student.find()
MongoDB Enterprise >