MongoDB学习笔记三—增删改文档上

插入insert

单条插入

> db.foo.insert({"bar":"baz"})
WriteResult({ "nInserted" : 1 })

批量插入

> db.foo.insert([{"_id":1},{"_id":2},{"_id":3}])
BulkWriteResult({
        "writeErrors" : [ ],
        "writeConcernErrors" : [ ],
        "nInserted" : 3,
        "nUpserted" : 0,
        "nMatched" : 0,
        "nModified" : 0,
        "nRemoved" : 0,
        "upserted" : [ ]
})
> db.foo.find()
{ "_id" : 1 }
{ "_id" : 2 }
{ "_id" : 3 }
> 

如果在执行批量插入的过程中有一个文档插入失败，那么在这个文档之前的所有文档都会插入成功，之后的所有全部失败。

> db.foo.insert([{"_id":10},{"_id":11},{"_id":10},{"_id":12}])
BulkWriteResult({
        "writeErrors" : [
                {
                        "index" : 2,
                        "code" : 11000,
                        "errmsg" : "E11000 duplicate key error collection: test.foo index: _id_ dup key: { : 10.0 }",
                        "op" : {
                                "_id" : 10
                        }
                }
        ],
        "writeConcernErrors" : [ ],
        "nInserted" : 2,
        "nUpserted" : 0,
        "nMatched" : 0,
        "nModified" : 0,
        "nRemoved" : 0,
        "upserted" : [ ]
})
> db.foo.find()
{ "_id" : 10 }
{ "_id" : 11 }
> 

删除文档

remove

remove函数接受一个查询文档作为参数。符合条件的文档才被删除。删除数据是永久性的，不能撤销，也不能恢复。

> db.foo.remove()
2016-12-15T19:50:31.721+0800 E QUERY    [thread1] Error: remove needs a query :
DBCollection.prototype._parseRemove@src/mongo/shell/collection.js:406:1
DBCollection.prototype.remove@src/mongo/shell/collection.js:433:18
@(shell):1:1

> db.foo.remove({"_id":10})
WriteResult({ "nRemoved" : 1 })
> db.foo.find()
{ "_id" : 11 }
> 

drop

要清空整个集合，那么使用drop直接删除集合会更快。代价是：不能指定任何限定条件。整个集合都被删除，所有元数据都不见了。

> for(var i=0;i<1000000;i++){
... db.tester.insert({"foo":"bar","baz":i,"z":10-i})
... }
WriteResult({ "nInserted" : 1 })
> db.tester.find()
{ "_id" : ObjectId("58528543b049609a5fa74f7c"), "foo" : "bar", "baz" : 0, "z" : 10 }
......

Type "it" for more
> db.tester.drop()//插入一百万条数据，使用drop删除,只需1ms
true
>

更新文档update

Update有两个必须参数：

一是查询文档，用于定位需要更新的目标文档

二是修改器文档，用于说明要找到的文档进行哪些修改

更新操作是不可分割的：若是两个更新同时发生，先到达服务器的先执行，接着执行另一个。

db.foo.insert({
... "name":"yyb",
... "friends":32,
... "enemies":2
... })
WriteResult({ "nInserted" : 1 })
> db.foo.update({"name":"yyb"},{"name":"joe"})//将yyb这个文档修改成{“name”:“joe”}
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.foo.find()
{ "_id" : ObjectId("58528a2bb049609a5fb691bc"), "name" : "joe" }
> 

文档替换

用一个新文档完全替换匹配的文档，这适合大规模模式迁移的情况。

  db.user.insert({
... ... "name":"joe",
... ... "friends":32,
... ... "enemies":2
... ... })
WriteResult({ "nInserted" : 1 })
//将上面这个文档的后两个字段移到子文档为realtionships中
> var joe=db.user.findOne({"name":"joe"})
> joe.relationships={"friends":joe.friends,"enemies":joe.enemies};
{ "friends" : 32, "enemies" : 2 }
> delete joe.friends
true
> delete joe.enemies
true
> db.user.update({"name":"joe"},joe);
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.user.find()
{ "_id" : ObjectId("58529188b049609a5fb691bf"), "name" : "joe", "relationships" : { "friends" : 32, "enemies" : 2 } }
> 

常见的错误是查询条件匹配到了多个文档，然后更新时由于第二个参数的存在就产生重复的 _id 值。数据库会抛出异常。

> db.user.find()
{ "_id" : ObjectId("585295e3b049609a5fb691c5"), "name" : "yyb", "age" : 21 }
{ "_id" : ObjectId("585295e3b049609a5fb691c6"), "name" : "yyb", "age" : 30 }
{ "_id" : ObjectId("585295e3b049609a5fb691c7"), "name" : "yyb", "age" : 40 }
> joe=db.user.findOne({"name":"yyb","age":30})
{ "_id" : ObjectId("585295e3b049609a5fb691c6"), "name" : "yyb", "age" : 30 }
> joe.age++;
30
> db.user.update({"name":"yyb"},joe)
WriteResult({
        "nMatched" : 0,
        "nUpserted" : 0,
        "nModified" : 0,
        "writeError" : {
                "code" : 16837,
                "errmsg" : "The _id field cannot be changed from {_id: ObjectId('585295e3b049609a5fb691c5')} to {_id: ObjectId('585295e3b049609a5fb691c6')}."
        }
})
> 

使用修改器

使用原子性的更新修改器，指定对文档的某些字段进行更新。更新修改器是种特殊的键，用来指定复杂的更新操作，比如修改、添加或者删除键，还可能是操作数组或者内嵌文档。

> db.user.find()
{ "_id" : ObjectId("585295e3b049609a5fb691c5"), "name" : "yyb", "age" : 21 }
{ "_id" : ObjectId("585295e3b049609a5fb691c6"), "name" : "yyb", "age" : 30 }
{ "_id" : ObjectId("585295e3b049609a5fb691c7"), "name" : "yyb", "age" : 40 }
> db.user.update({"name":"yyb"},{$inc:{"age":5}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })> db.user.find({"name":"yyb"})
{ "_id" : ObjectId("585295e3b049609a5fb691c5"), "name" : "yyb", "age" : 26 }
{ "_id" : ObjectId("585295e3b049609a5fb691c6"), "name" : "yyb", "age" : 30 }
{ "_id" : ObjectId("585295e3b049609a5fb691c7"), "name" : "yyb", "age" : 40 }
> 

明明匹配3条，却只改了一条。原来MongoDB默认只会更新匹配的第一条，如果要更新多条，还得指定参数。

使用修改器时，_id的值不能改变。（整个文档替换时可以改变“_id”）

$set与$unset

用来指定一个字段的值。如果这个字段不存在，则创建它。

> db.user.insert({
... "name":"yyb",
... "age":20,
... "sex":"male",
... "location":"cd"})
WriteResult({ "nInserted" : 1 })
>> db.user.update({"name":"yyb"},{"$set":{"email":"123@qq.com"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.user.find().pretty()
{
        "_id" : ObjectId("58529e66b049609a5fb691c9"),
        "name" : "yyb",
        "age" : 20,
        "sex" : "male",
        "location" : "cd",
        "email" : "123@qq.com"
}
> 

用 $set 甚至可以修改键的类型。用 $unset 可以将键完全删除。

>  db.user.update(
... ... {"name":"yyb"},
... ... {"$set":{"email":["xx@qq.com","xl@sina.com"]}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.user.find().pretty()
{
        "_id" : ObjectId("58529e66b049609a5fb691c9"),
        "name" : "yyb",
        "age" : 20,
        "sex" : "male",
        "location" : "cd",
        "email" : [
                "xx@qq.com",
                "xl@sina.com"
        ]
}
> db.user.update({"name":"yyb"},{"$unset":{"email":1}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.user.find().pretty()
{
        "_id" : ObjectId("58529e66b049609a5fb691c9"),
        "name" : "yyb",
        "age" : 20,
        "sex" : "male",
        "location" : "cd"
}

也可以用 $set 修改内嵌文档：

{
        "_id" : ObjectId("5853e17ff7720722b4ded850"),
        "title" : "a blog post",
        "content" : "...",
        "author" : {
                "name" : "yyb",
                "email" : "aaa@sina.com"
        }
}
> db.blog.update(
... {"author.name":"yyb"},
... {"$set":{"author.name":"joe"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.blog.findOne()
{
        "_id" : ObjectId("5853e17ff7720722b4ded850"),
        "title" : "a blog post",
        "content" : "...",
        "author" : {
                "name" : "joe",
                "email" : "aaa@sina.com"
        }
}

增加、删除、修改键时，应该使用$开头的修改器，否则可能会将整个文档替换掉。

$inc

 $inc 用来增加已有键的值，或者该键不存在那就创建一个。对于更新分析数据、因果关系、投票或者其他有变化数值的地方很方便。

> db.games.insert({"games":"pinball","user":"joe"})
WriteResult({ "nInserted" : 1 })
> db.games.update({"games":"pinball"},{"$inc":{"score":50}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.games.findOne()
{
        "_id" : ObjectId("5853e517f7720722b4ded851"),
        "games" : "pinball",
        "user" : "joe",
        "score" : 50
}
> db.games.update({"games":"pinball"},{"$inc":{"score":10000}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.games.findOne()
{
"_id" : ObjectId("5853e517f7720722b4ded851"),
"games" : "pinball",
"user" : "joe",
"score" : 10050
}
>

 $inc 就是专门用来增减数字的。且只能用于整型、长整型或者双精度浮点型的值。其他类型的数据会操作失败。

> db.foo.insert({"count":"1"})
WriteResult({ "nInserted" : 1 })

> db.foo.update({},{"$inc":{"count":1}})
WriteResult({
        "nMatched" : 0,
        "nUpserted" : 0,
        "nModified" : 0,
        "writeError" : {
                "code" : 16837,
                "errmsg" : "Cannot apply $inc to a value of non-numeric type. {_id: ObjectId('5853e73df7720722b4ded853')} has the field 'count' of non-numeric type String"
        }
})
> 

 $inc 键的值必须为数字”，不能使用字符串、数组或者其他非数字的值。要修改其他类型，应该使用 $set 或者数字修改器。

> db.foo.insert({"count":1})
WriteResult({ "nInserted" : 1 })

> db.foo.update({},{"$inc":{"count":"5"}})
WriteResult({
        "nMatched" : 0,
        "nUpserted" : 0,
        "nModified" : 0,
        "writeError" : {
                "code" : 14,
                "errmsg" : "Cannot increment with non-numeric argument: {count: "5"}"
        }
})
> 

数组修改器

$push

$push 添加元素。如果数组已经存在，会向已有的数组末尾加入一个元素，要是没有就创建一个新的数组。

> db.blog.post.findOne()
{
        "_id" : ObjectId("5853ea01f7720722b4ded855"),
        "title" : "a blog post",
        "content" : "..."
}
> db.blog.post.update(
... {"title":"a blog post"},
... {"$push":{"comments":{"name":"joe","email":"joe@qq.com","content":"nice post"}}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.blog.post.findOne()
{
        "_id" : ObjectId("5853ea01f7720722b4ded855"),
        "title" : "a blog post",
        "content" : "...",
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@qq.com",
                        "content" : "nice post"
                }
        ]
}
> 

> db.blog.post.update(
... {"title":"a blog post"},
... {"$push":{"comments":{"name":"bob","email":"bob@sina.com","content":"good post."}}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.blog.post.findOne()
{
        "_id" : ObjectId("5853ea01f7720722b4ded855"),
        "title" : "a blog post",
        "content" : "...",
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@qq.com",
                        "content" : "nice post"
                },
                {
                        "name" : "bob",
                        "email" : "bob@sina.com",
                        "content" : "good post."
                }
        ]
}
> 

$each

可以将它应用在一些比较复杂的数组操作中。使用 $each 子操作符，可以通过一次 $push 操作添加多个值。

比如：下面将三个新元素添加到数组中。如果指定的数组中只包含一个元素，那么等同于和没有使用“$each”的普通的“$push”操作。

db.stock.ticket.insert({"_id":"goog"})
WriteResult({ "nInserted" : 1 })
>  db.stock.ticket.update(
... ... ... {"_id":"goog"},
... ... ... {"$push":{"hourly":{"$each":[562.776,562.790,559.123]}}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.stock.ticket.findOne()
{ "_id" : "goog", "hourly" : [ 562.776, 562.79, 559.123 ] }

要实现上面的操作，下面方法也可以。

db.stock.ticket.update(
... ... ... ... ... {"_id":"goog"},
... ... ... ... ... {"$set":{"hourly":[562.776,562.790,559.123]}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.stock.ticket.findOne()
{ "_id" : "goog", "hourly" : [ 562.776, 562.79, 559.123 ] }

而下面这样是不行的

 db.stock.ticket.update(
... ... ... ... {"_id":"goog"},
... ... ... ... {"$push":{"hourly":[562.776,562.790,559.123]}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.stock.ticket.findOne()
{ "_id" : "goog", "hourly" : [ [ 562.776, 562.79, 559.123 ] ] }