mongodb 的update方法

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的對象和一些更新的操作符（如$,$inc...）等，也可以理解爲sql update查詢內set後面的
upsert   : 這個參數的意思是，如果不存在update的記錄，是否插入objNew,true爲插入，默認是false，不插入。
multi    : mongodb默認是false,只更新找到的第一條記錄，如果這個參數爲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就是要更新的對象，只能是單條記錄。

如果在collection內已經存在一個和x對象相同的"_id"的記錄。mongodb就會把x對象替換collection內已經存在的記錄，否則將會插入x對象，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 } }

就是相當於sql的set field = value，全部數據類型都支持$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} }

顧名思義，就是刪除字段了。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" }

沒看出field : 1裏面的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裏面去，field一定要是數組類型纔行，如果field不存在，會新增一個數組類型加進去。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字段內。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 } }

增加一個值到數組內，而且只有當這個值不在數組內才增加。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" }


<strong>7) $pop</strong>

刪除數組內的一個值

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及以後的版本纔可以用，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" }

<strong>8) $pull</strong>

用法：$pull : { field : value } }

從數組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" }

<strong>9) $pullAll</strong>

用法：{ $pullAll : { field : value_array } }

同$pull,可以一次刪除數組內的多個值。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" }


<strong>10) $ 操作符
</strong>
$是他自己的意思，代表按條件找出的數組裏面某項他自己。呵呵，比較坳口。看一下官方的例子：

> t.find()
{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4b97e62bf1d8c7152c9ccb74"</span>), <span class="code-quote">"title"</span> : <span class="code-quote">"ABC"</span>,  <span class="code-quote">"comments"</span> : [ { <span class="code-quote">"by"</span> : <span class="code-quote">"joe"</span>, <span class="code-quote">"votes"</span> : 3 }, { <span class="code-quote">"by"</span> : <span class="code-quote">"jane"</span>, <span class="code-quote">"votes"</span> : 7 } ] }

> t.update( {'comments.by':'joe'}, {$inc:{'comments.$.votes':1}}, <span class="code-keyword">false</span>, <span class="code-keyword">true</span> )

> t.find()
{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4b97e62bf1d8c7152c9ccb74"</span>), <span class="code-quote">"title"</span> : <span class="code-quote">"ABC"</span>,  <span class="code-quote">"comments"</span> : [ { <span class="code-quote">"by"</span> : <span class="code-quote">"joe"</span>, <span class="code-quote">"votes"</span> : 4 }, { <span class="code-quote">"by"</span> : <span class="code-quote">"jane"</span>, <span class="code-quote">"votes"</span> : 7 } ] }

需要注意的是，$只會應用找到的第一條數組項，後面的就不管了。還是看例子：

> t.find();
{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4b9e4a1fc583fa1c76198319"</span>), <span class="code-quote">"x"</span> : [ 1, 2, 3, 2 ] }
> t.update({x: 2}, {$inc: {<span class="code-quote">"x.$"</span>: 1}}, <span class="code-keyword">false</span>, <span class="code-keyword">true</span>);
> t.find();

還有注意的是$配合$unset使用的時候，會留下一個null的數組項，不過可以用{$pull:{x:null}}刪除全部是null的數組項。例：
> t.insert({x: [1,2,3,4,3,2,3,4]})
> t.find()
{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4bde2ad3755d00000000710e"</span>), <span class="code-quote">"x"</span> : [ 1, 2, 3, 4, 3, 2, 3, 4 ] }
> t.update({x:3}, {$unset:{<span class="code-quote">"x.$"</span>:1}})
> t.find()
{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4bde2ad3755d00000000710e"</span>), <span class="code-quote">"x"</span> : [ 1, 2, <span class="code-keyword">null</span>, 4, 3, 2, 3, 4 ] }

{ <span class="code-quote">"_id"</span> : ObjectId(<span class="code-quote">"4b9e4a1fc583fa1c76198319"</span>), <span class="code-quote">"x"</span> : [ 1, 3, 3, 2 ] }

mongodb 的update方法

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