//转载
1).update()命令
db.collection.update( criteria, objNew, upsert, multi )
criteria : update的查询条件，类似sql update查询内where后面的
objNew : update的对象和一些更新的操作符（如$,$inc...）等，也可以理解为sql update查询内set后面的
upsert : 这个参数的意思是，如果不存在update的记录，是否插入objNew,true为插入，默认是false，不插入。
multi : mongodb默认是false,只更新找到的第一条记录，如果这个参数为true,就把按条件查出来多条记录全部更新。
例：
db.test0.update( { "count" : { $gt : 1 } } , { $set : {
"test2" : "OK"} } ); 只更新了第一条记录
db.test0.update( { "count" : { $gt : 3 } } , { $set : {
"test2" : "OK"} },false,true ); 全更新了
db.test0.update( { "count" : { $gt : 4 } } , { $set : {
"test5" : "OK"} },true,false ); 只加进去了第一条
db.test0.update( { "count" : { $gt : 5 } } , { $set : {
"test5" : "OK"} },true,true ); 全加进去了
db.test0.update( { "count" : { $gt : 15 } } , { $inc : {
"count" : 1} },false,true );全更新了
db.test0.update( { "count" : { $gt : 10 } } , { $inc : {
"count" : 1} },false,false );只更新了第一条
2).save()命令
db.collection.save( x )
x就是要更新的对象，只能是单条记录。
如果在collection内已经存在一个和x对象相同的"_id"的记录。mongodb就会把x对象替换collection内已经存在的记录，否则将会插入x对象，如果x内没有_id,系统会自动生成一个再插入。相当于上面update语句的upsert=true,multi=false的情况。
例：
db.test0.save({count:40,test1:"OK"}); #_id系统会生成
db.test0.save({_id:40,count:40,test1:"OK"}); #如果test0内有_id等于40的，会替换，否则插入。
mongodb的更新操作符：
1) $inc
用法：{ $inc : { field : value } }
意思对一个数字字段field增加value，例：
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 16,
"test1" : "TESTTEST", "test2" : "OK",
"test3" : "TESTTEST", "test4" : "OK",
"test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $inc : { "count" :
1 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 17,
"test1" : "TESTTEST", "test2" : "OK",
"test3" : "TESTTEST", "test4" : "OK",
"test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $inc : { "count" :
2 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 19,
"test1" : "TESTTEST", "test2" : "OK",
"test3" : "TESTTEST", "test4" : "OK",
"test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $inc : { "count" :
-1 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : "TESTTEST", "test2" : "OK",
"test3" : "TESTTEST", "test4" : "OK",
"test5" : "OK" }
2) $set
用法：{ $set : { field : value } }
就是相当于sql的set field = value，全部数据类型都支持$set。例：
> db.test0.update( { "_id" : 15 } , { $set : { "test1" :
"testv1","test2" : "testv2","test3" :
"testv3","test4" : "testv4" } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : "testv1", "test2" : "testv2",
"test3" : "testv3", "test4" : "testv4",
"test5" : "OK" }
3) $unset
用法：{ $unset : { field : 1} }
顾名思义，就是删除字段了。例：
> db.test0.update( { "_id" : 15 } , { $unset : {
"test1":1 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test2" : "testv2", "test3" : "testv3",
"test4" : "testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $unset : {
"test2": 0 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test3" : "testv3", "test4" : "testv4",
"test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $unset : {
"test3":asdfasf } } );
Fri May 14 16:17:38 JS Error: ReferenceError: asdfasf is not defined (shell):0
> db.test0.update( { "_id" : 15 } , { $unset : { "test3":"test"
} } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test4" : "testv4", "test5" : "OK" }
没看出field : 1里面的1是干什么用的，反正只要有东西就行。
4) $push
用法：{ $push : { field :
value } }
把value追加到field里面去，field一定要是数组类型才行，如果field不存在，会新增一个数组类型加进去。例：
> db.test0.update( { "_id" : 15 } , { $set : { "test1" :
["aaa","bbb"] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $push : { "test1":
"ccc" } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc" ],
"test4" : "testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $push : { "test2":
"ccc" } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc" ],
"test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $push : { "test1":
["ddd","eee"] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc", [
"ddd", "eee" ] ], "test2" : [ "ccc" ],
"test4" : "testv4", "test5" : "OK" }
5) $pushAll
用法：{ $pushAll : { field : value_array } }
同$push,只是一次可以追加多个值到一个数组字段内。例：
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc", [
"ddd", "eee" ] ], "test2" : [ "ccc" ],
"test4" : "testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $pushAll : {
"test1": ["fff","ggg"] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc", [
"ddd", "eee" ], "fff", "ggg" ],
"test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
6) $addToSet
用法：{ $addToSet : {
field : value } }
增加一个值到数组内，而且只有当这个值不在数组内才增加。例：
> db.test0.update( { "_id" : 15 } , { $addToSet : {
"test1": {$each : ["444","555"] } } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb" , "ccc", [ "ddd", "eee" ], "fff", "ggg", [ "111", "222" ],
"444", "555"], "test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $addToSet : {
"test1": {$each : ["444","555"] } } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : ["aaa", "bbb", "ccc", [ "ddd", "eee" ], "fff", "ggg", [ "111", "222" ], "444", "555" ], "test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $addToSet : {
"test1": ["444","555"] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa",
"bbb", "ccc", ["ddd", "eee" ], "fff", "ggg", [ "111", "222" ], "444", "555", [ "444", "555"]], "test2" : [ "ccc" ], "test4" : testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $addToSet : {
"test1": ["444","555"] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "aaa", "bbb", "ccc", [ "ddd", "eee" ], "fff", "ggg", [ "111", "222" ], "444", "555", [ "444", "555" ]], "test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
7) $pop
删除数组内的一个值
用法：
删除最后一个值：{ $pop : { field : 1 } }
删除第一个值：{ $pop : {
field : -1 } }
注意，只能删除一个值，也就是说只能用1或-1，而不能用2或-2来删除两条。mongodb
1.1及以后的版本才可以用，例：
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "bbb", "ccc", [ "ddd", "eee" ], "fff", "ggg", [ "111", "222" ], "444"], "test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $pop : { "test1":
-1 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "ccc", [ "ddd", "eee" ], "fff", "ggg", [ "111", "222"], "444"], "test2" : [ "ccc" ], "test4" :
"testv4", "test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $pop : { "test1":
1 } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "ccc", [ "ddd", "eee" ],
"fff", "ggg", [ "111", "222" ] ],
"test2" : [ "ccc" ], "test4" :
"testv4",
"test5" : "OK" }
8) $pull
用法：$pull : { field : value } }
从数组field内删除一个等于value值。例：
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "ccc", [ "ddd", "eee" ],
"fff", "ggg", [ "111", "222" ] ],
"test2" : [ "ccc" ], "test4" :
"testv4",
"test5" : "OK" }
> db.test0.update( { "_id" : 15 } , { $pull : { "test1":
"ggg" } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "ccc", [ "ddd", "eee" ],
"fff", [ "111", "222" ] ], "test2" : [
"ccc" ], "test4" : "testv4", "test5"
: "OK" }
9) $pullAll
用法：{ $pullAll : { field : value_array } }
同$pull,可以一次删除数组内的多个值。例：
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ "ccc", [ "ddd", "eee" ],
"fff", [ "111", "222" ] ], "test2" : [
"ccc" ], "test4" : "testv4", "test5"
: "OK" }
> db.test0.update( { "_id" : 15 } , { $pullAll : {
"test1": [ "ccc" , "fff" ] } } );
> db.test0.find( { "_id" : 15 } );
{ "_id" : { "floatApprox" : 15 }, "count" : 18,
"test1" : [ [ "ddd", "eee" ], [ "111",
"222" ] ], "test2" : [ "ccc" ], "test4"
: "testv4", "test5" : "OK" }
10) $ 操作符
$是他自己的意思，代表按条件找出的数组里面某项他自己。呵呵，比较坳口。看一下官方的例子：
> t.find()
{ "_id" : ObjectId("4b97e62bf1d8c7152c9ccb74"),
"title" : "ABC",
"comments" : [ { "by" : "joe",
"votes" : 3 }, { "by" : "jane", "votes"
: 7 } ] }
> t.update( {‘comments.by‘:‘joe‘}, {$inc:{‘comments.$.votes‘:1}}, false,
true )
> t.find()
{ "_id" : ObjectId("4b97e62bf1d8c7152c9ccb74"),
"title" : "ABC",
"comments" : [ { "by" : "joe",
"votes" : 4 }, { "by" : "jane", "votes"
: 7 } ] }
需要注意的是，$只会应用找到的第一条数组项，后面的就不管了。还是看例子：
> t.find();
{ "_id" : ObjectId("4b9e4a1fc583fa1c76198319"),
"x" : [ 1, 2, 3, 2 ] }
> t.update({x: 2}, {$inc: {"x.$": 1}}, false, true);
> t.find();
还有注意的是$配合$unset使用的时候，会留下一个null的数组项，不过可以用{$pull:{x:null}}删除全部是null的数组项。例：
> t.insert({x: [1,2,3,4,3,2,3,4]})
> t.find()
{ "_id" : ObjectId("4bde2ad3755d00000000710e"),
"x" : [ 1, 2, 3, 4, 3, 2, 3, 4 ] }
> t.update({x:3}, {$unset:{"x.$":1}})
> t.find()
{ "_id" : ObjectId("4bde2ad3755d00000000710e"),
"x" : [ 1, 2, null, 4, 3, 2, 3, 4 ] }
{ "_id" : ObjectId("4b9e4a1fc583fa1c76198319"),
"x" : [ 1, 3, 3, 2 ] }