CRUD 操作

• 与 SQL 对应的关系

SQL	MongoDB
database	database
table	collection
row	document
column	field
index	index
joins	无表连接，使用嵌入式文档替代
primary key	primary key

以下操作均是对于 document

增

db.COLLECTION_NAME.insertOne(
   <document>,
   {
      writeConcern: <document>
   }
)

db.COLLECTION_NAME.insertMany(
   [ <document 1> , <document 2>, ... ],
   {
      writeConcern: <document>,
      ordered: <boolean>
   }
)

插入单条数据, 这里没有显式的创建 user 集合，直接执行插入语句会判断是否存在该集合，没有该集合会自动创建，插入的时候没有指定 _id 则会自动分配 ObjectId

miodb> db.user.insertOne({"name":"miomiora", "age":24, "gender":"男"})
{
  acknowledged: true,
  insertedId: ObjectId("641fba25e438a9958f14131a")
}

miodb> db.user.insertMany([{"name":"akiyama", "age":17, "gender":"女"},{"name":"yui", "age":16, "gender":"女"},{"name":"hanamaru", "age":19, "gender":"女"},{"name":"makoto", "age":51, "gender":"男"}])
{
  acknowledged: true,
  insertedIds: {
    '0': ObjectId("641fbad6e438a9958f14131b"),
    '1': ObjectId("641fbad6e438a9958f14131c"),
    '2': ObjectId("641fbad6e438a9958f14131d"),
    '3': ObjectId("641fbad6e438a9958f14131e")
  }
}

查

查询语句 db.COLLECTION_NAME.find(<query>, [projection]，其中 findOne()方法只返回一个文档

miodb> db.user.findOne()
{
    _id: ObjectId("641fba25e438a9958f14131a"),
    name: 'miomiora',
    age: 24,
    gender: '男'
}

miodb> db.user.find()
[
  {
    _id: ObjectId("641fba25e438a9958f14131a"),
    name: 'miomiora',
    age: 24,
    gender: '男'
  },
  {
    _id: ObjectId("641fbad6e438a9958f14131b"),
    name: 'akiyama',
    age: 17,
    gender: '女'
  },
  {
    _id: ObjectId("641fbad6e438a9958f14131c"),
    name: 'yui',
    age: 16,
    gender: '女'
  },
  {
    _id: ObjectId("641fbad6e438a9958f14131d"),
    name: 'hanamaru',
    age: 19,
    gender: '女'
  },
  {
    _id: ObjectId("641fbad6e438a9958f14131e"),
    name: 'makoto',
    age: 51,
    gender: '男'
  }
]

改

db.COLLECTION_NAME.updateOne(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>      
   }
)

db.COLLECTION_NAME.updateMany(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>      
   }
)

把所有性别为 男 的文档改为 女, $set 表示只替换后面的键值对

miodb> db.user.updateMany({gender:"男"}, {$set:{gender:"女"}})
{
  acknowledged: true,
  insertedId: null,
  matchedCount: 2,
  modifiedCount: 2,
  upsertedCount: 0
}

删

# 此外还有 deleteMany() 方法
db.COLLECTION_NAME.deleteOne(
   <filter>,
   {
      writeConcern: <document>,
      collation: <document>,
      hint: <document|string>
   }
)

示例

miodb> db.user.deleteOne({gender:"女"})
{ acknowledged: true, deletedCount: 1 }