對於文檔的更新除替換外，針對某個或多個文檔只需要部分更新可使用原子的更新修改器，能夠高效的進行文檔更新。更新修改器是中特殊的鍵，用來指定複雜的操作，比如增加、刪除或者調整鍵，還可能是操作數組或者內嵌文檔。1.$inc--------------------------------------------------------------------------這個修改器幹什麼使的呢？看看下面示例的具體操作後的結果即可知道。示例文檔：{"uid":"201203","type":"1",size:10}>
db.b.insert({"uid":"201203","type":"1",size:10})>
db.b.find(){
"_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1","size"
: 10 }>
db.b.update({"uid" : "201203"},{"$inc":{"size" : 1}})>
db.b.find(){
"_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1","size"
: 11 }>
db.b.update({"uid" : "201203"},{"$inc":{"size" : 2}})>
db.b.find(){
"_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1","size"
: 13 }>
db.b.update({"uid" : "201203"},{"$inc":{"size" : -1}})>
db.b.find(){
"_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1","size"
: 12 }得出結論：修改器$inc可以對文檔的某個值爲數字型（只能爲滿足要求的數字）的鍵進行增減的操作。（這裏有個問題：上篇中說到更新默認只對滿足條件的記錄集中第一個文檔進行更新，那麼使用$inc修改器之後，還是一樣嗎？）2.$set-------------------------------------------------------------------用來指定一個鍵並更新鍵值，若鍵不存在並創建。來看看下面的效果：>
db.a.findOne({"uid" : "20120002","type" : "3"}){
"_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num":
40, "sname" : "jk", "type" : "3", "uid" : "20120002" }--size鍵不存在的場合>
db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"size":10}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){
"_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num":
40, "size" : 10, "sname" : "jk", "type" : "3", "uid" : "20120002" }==========================================================================================--這裏size鍵不存在，但也並沒有自動創建記錄啊--sname鍵存在的場合>
db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"sname":"ssk"}})>
db.a.find(){
"_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num":
40, "size" : 10, "sname" : "ssk", "type" : "3", "uid" : "20120002" }{
"_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num":
50, "sname" : "jk", "type" : "1", "uid" : "20120002" }--可改變鍵的值類型>
db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"sname":["java",".net","c++"]}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){ "_id"
: ObjectId("500216de81b954b6161a7d8f"), "desc"
: "hello world2!", "num"
: 40, "size"
: 10, "sname"
: [ "java", ".net", "c++" ], "type"
: "3", "uid"
: "20120002"}對於內嵌的文檔，$set又是如何進行更新的內嵌的文檔的呢，請看下面的示例：示例文檔：{"name":"toyota","type":"suv","size":{"height":10,"width":5,"length":15}}>
db.c.findOne({"name":"toyota"}){ "_id"
: ObjectId("5003be465af21ff428dafbe7"), "name"
: "toyota", "type"
: "suv", "size"
: { "height"
: 10, "width"
: 5, "length"
: 15 }}>
db.c.update({"name":"toyota"},{"$set":{"size.height":8}})>
db.c.findOne({"name":"toyota"}){ "_id"
: ObjectId("5003be465af21ff428dafbe7"), "name"
: "toyota", "type"
: "suv", "size"
: { "height"
: 8, "width"
: 5, "length"
: 15 }}>
db.c.update({"name":"toyota"},{"$set":{"size.width":7}})>
db.c.findOne({"name":"toyota"}){ "_id"
: ObjectId("5003be465af21ff428dafbe7"), "name"
: "toyota", "type"
: "suv", "size"
: { "height"
: 8, "width"
: 7, "length"
: 15 }}可見：對於內嵌文檔在使用$set更新時，使用"."連接的方式。3.$unset----------------------------------------------------------------從字面就可以看出其意義，主要是用來刪除鍵。示例操作效果如下：>
db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"sname":1}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){ "_id"
: ObjectId("500216de81b954b6161a7d8f"), "desc"
: "hello world2!", "num"
: 40, "size"
: 10, "type"
: "3", "uid"
: "20120002"}>
db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"num":0}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){ "_id"
: ObjectId("500216de81b954b6161a7d8f"), "desc"
: "hello world2!", "size"
: 10, "type"
: "3", "uid"
: "20120002"}>
db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"size":-1}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){ "_id"
: ObjectId("500216de81b954b6161a7d8f"), "desc"
: "hello world2!", "type"
: "3", "uid"
: "20120002"}>
db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"desc":"sssssss"}})>
db.a.findOne({"uid" : "20120002","type" : "3"}){ "_id"
: ObjectId("500216de81b954b6161a7d8f"), "type"
: "3", "uid"
: "20120002"}得出結論：使用修改器$unset時，不論對目標鍵使用1、0、-1或者具體的字符串等都是可以刪除該目標鍵。4.數組修改器--$push------------------------------------------------------------------示例操作效果如下：>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "type" : "suv",
"size"
: { "height" : 8, "width" : 7, "length" : 15 } }--先push一個當前文檔中不存在的鍵title>
db.c.update({"name" : "toyota"},{$push:{"title":"t1"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1" ], "type" : "suv" } --再向title中push一個值>
db.c.update({"name" : "toyota"},{$push:{"title":"t2"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2" ], "type" : "suv" }--再向title中push一個值>
db.c.update({"name" : "toyota"},{$push:{"title":"t2"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }--再向一個已經存在的鍵值非數組類型的鍵push一個值>
db.c.update({"name" : "toyota"},{$push:{"size.height":10}})Cannot
apply $push/$pushAll modifier to non-array>
db.c.update({"name" : "toyota"},{$push:{"name":"ddddddd"}})Cannot
apply $push/$pushAll modifier to non-array得出結論：$push--向文檔的某個數組類型的鍵添加一個數組元素，不過濾重複的數據。添加時鍵存在，要求鍵值類型必須是數組；鍵不存在，則創建數組類型的鍵。5.數組修改器--$ne/$addToSet---------------------------------------------------------------------主要給數組類型鍵值添加一個元素時，避免在數組中產生重複數據，$ne在有些情況是不通行的。>
db.c.update({"title" : {$ne:"t2"}},{$push:{"title":"t2"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }>
db.c.update({"name" : "toyota"},{$addToSet:{"title":"t2"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }6.數組修改器--$pop、$pull------------------------------------------------------------$pop從數組的頭或者尾刪除數組中的元素，示例如下：{
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t3", "t4" ],"type" : "suv" }--從數組的尾部刪除
1>
db.c.update({"name" : "toyota"},{$pop:{"title":1}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t3" ], "type" : "suv" }--從數組的頭部
-1>
db.c.update({"name" : "toyota"},{$pop:{"title":-1}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t2", "t3" ], "type" : "suv" }--從數組的尾部刪除
0>
db.c.update({"name" : "toyota"},{$pop:{"title":0}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t2" ], "type" : "suv" } $pull從數組中刪除滿足條件的元素，示例如下：{
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t2", "t2", "t3" ],"type" : "suv" } >
db.c.update({"name" : "toyota"},{$pull:{"title":"t2"}})>
db.c.find(){
"_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8, "width"
: 7, "length" : 15 }, "title" : [ "t1", "t3" ], "type" : "suv" }7.數組的定位修改器-------------------------------------------------------------------在需要對數組中的值進行操作的時候，可通過位置或者定位操作符（"$"）.數組是0開始的，可以直接將下標作爲鍵來選擇元素。示例如下：{"uid":"001",comments:[{"name":"t1","size":10},{"name":"t2","size":12}]}>
db.c.find({"uid":"001"}){
"_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {"name"
: "t1", "size" : 10 }, { "name" : "t2", "size" : 12 } ] }>
db.c.update({"uid":"001"},{$inc:{"comments.0.size":1}})>
db.c.find({"uid":"001"}){
"_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {"name"
: "t1", "size" : 11 }, { "name" : "t2", "size" : 12 } ] }>
db.c.update({"comments.name":"t1"},{$set:{"comments.$.size":1}})>
db.c.find({"uid":"001"}){
"_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {"name"
: "t1", "size" : 1 }, { "name" : "t2", "size" : 12 } ] }--若爲多個文檔滿足條件，則只更新第一個文檔。8.upsert-----------------------------------------------------------------upsert是一種特殊的更新。當沒有符合條件的文檔，就以這個條件和更新文檔爲基礎創建一個新的文檔，如果找到匹配的文檔就正常的更新。使用upsert，既可以避免競態問題，也可以減少代碼量（update的第三個參數就表示這個upsert，參數爲true時）>
db.c.remove()>
db.c.update({"size":11},{$inc:{"size":3}})>
db.c.find()>
db.c.update({"size":11},{$inc:{"size":3}},false)>
db.c.find()>
db.c.update({"size":11},{$inc:{"size":3}},true)>
db.c.find(){
"_id" : ObjectId("5003ded6c28f67507a6df1de"), "size" : 14 }9.save函數-----------------------------------------------------------------1.可以在文檔不存在的時候插入，存在的時候更新，只有一個參數文檔。2.要是文檔含有"_id"，會調用upsert。否則，會調用插入。>
db.a.find(){
"_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num": 50, "sname"
: "jk", "type" : "1", "uid" : "20120002" }>
var o = db.a.findOne()>
o.num = 5555>
db.a.save(o)>
db.a.find(){
"_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num": 55, "sname"
: "jk", "type" : "1", "uid" : "20120002" }