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mongodb 更新操作

在前面的文章“mongodb 查詢的語法”裡,我介紹了Mongodb的常用查詢語法,Mongodb的update操作也有點複雜,我結合自己的使用經驗,在這裡介紹一下,給用mongodb的朋友看看,也方便以後自己用到的時候查閱:

注:在這篇文章及上篇文章內講的語法介紹都是在mongodb shell環境內的,和真正運用語言程式設計(如java,php等)使用時,在使用方法上會有一些差別,但語法(如查詢條件,$in,$inc等)是一樣的。

本文是參考官方文件來介紹的,之所以有官方文件還要在這介紹,一方面是就當翻譯,畢竟每次要用時去看英文文件比較累,第二是官方文件講解比較簡單,有時光看官方文件不好理解,我在實際操作的情況下可以做些補充。

好了,不多說了,下面正式開始:

mongodb更新有兩個命令:

1).update()命令


db.collection.update( criteria, objNew, upsert, multi )

criteria : update的查詢條件,類似sql update查詢內where後面的
objNew   : update的物件和一些更新的操作符(如$,$inc...)等,也可以理解為sql update查詢內set後面的
upsert   : 這個引數的意思是,如果不存在update的記錄,是否插入objNew,true為插入,預設是false,不插入。
multi    : mongodb預設是false,只更新找到的第一條記錄,如果這個引數為true,就把按條件查出來多條記錄全部更新。

例:
db.test0.update( { "count" : { $gt : 1 } } , { $set : { "test2" : "OK"} } ); 只更新了第一條記錄
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 ); 只加進去了第一條
db.test0.update( { "count" : { $gt : 5 } } , { $set : { "test5" : "OK"} },true,true ); 全加進去了
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 );只更新了第一條

2).save()命令


db.collection.save( x )

x就是要更新的物件,只能是單條記錄。

如果在collection內已經存在一個和x物件相同的"_id"的記錄。mongodb就會把x物件替換collection內已經存在的記錄,否則將會插入x物件,如果x內沒有_id,系統會自動生成一個再插入。相當於上面update語句的upsert=true,multi=false的情況。

例:
db.test0.save({count:40,test1:"OK"}); #_id系統會生成
db.test0.save({_id:40,count:40,test1:"OK"}); #如果test0內有_id等於40的,會替換,否則插入。


mongodb的更新操作符:

1) $inc


用法:{ $inc : { field : value } }

意思對一個數字欄位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 } }

就是相當於sql的set field = value,全部資料型別都支援$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} }

顧名思義,就是刪除欄位了。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" }

沒看出field : 1裡面的1是幹什麼用的,反正只要有東西就行。


4) $push

用法:{ $push : { field : value } }

把value追加到field裡面去,field一定要是陣列型別才行,如果field不存在,會新增一個數組型別加進去。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個值到一個數組欄位內。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 } }

增加一個值到陣列內,而且只有當這個值不在陣列內才增加。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

刪除陣列內的一個值

用法:
刪除最後一個值:{ $pop : { field : 1  } }
刪除第一個值:{ $pop : { field : -1  } }

注意,只能刪除一個值,也就是說只能用1或-1,而不能用2或-2來刪除兩條。mongodb 1.1及以後的版本才可以用,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 } }

從陣列field內刪除一個等於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,可以一次刪除陣列內的多個值。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,代表按條件找出的數組裡面某項他自己。呵呵,比較坳口。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,$只會應用找到的第一條陣列項,後面的就不管了。還是看例子:

> t.find();
{ "_id" : ObjectId("4b9e4a1fc583fa1c76198319"), "x" : [ 1, 2, 3, 2 ] }
> t.update({x: 2}, {$inc: {"x.$": 1}}, false, true);
> t.find();

還有注意的是$配合$unset使用的時候,會留下一個null的陣列項,不過可以用{$pull:{x:null}}刪除全部是null的陣列項。例:
> t.insert({x: [1,2,3,4,3,2,3,4]})
> t.find()
{ "_id" : ObjectId("4bde2ad3755d00000000710e"), "x" : [ 1, 2, 3, 4, 3, 2, 3, 4 ] }
> t.update({x:3}, {$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 ] }