('test').collection('mycollection'); collection.find({ field: 'test' }).toArray((err, docs) => { if (err) throw err; if (docs.length > 0) { console.log('Value exists in collection'); } else { console.log('Value does not exist in collection'); } client.close(); }); })...
db.test.aggregate([{$match: {_:ISODate("2015-06-01"), "H": "id", "12345678": {"$exists": true}, "I": "XXX"}}, {$group: {_id: {"12345678": "$12345678", "G": "$G"}, "value": {"$sum": 1}}}], {allowDiskUse:true}) 38、修改Key:Value中的Value 给字段B的值加上...
().length); }) //创建索引 db.col.createIndex({"field3":1},{background:true}); //进入数据库查看当前索引创建线程状态 db.adminCommand({ currentOp: true, $or: [ { op: "command", "command.createIndexes": { $exists: true }}, { op: "none", "msg" : /^Index Build/ }]}) //...
43、更换Key: Value中的Key verRelease 换为TEST db.test.find().forEach(function(item){db.test.update({_id:item["_id"]}, {"$set": {"TEST": item["verRelease"]}}, {"$unset":{"verRelease":{"exists":true}}})}) 或者更新部分修改为: db.test.update({D : ISODate("2014-11-02")...
MongoDB 的主要目标是在 key-value (键/值)存储方式(提供了高性能和高度伸缩性)以及传统的 RDBMS 系统(丰富的功能)架起一座桥梁,集两者的优势于一身。 MongoDB 适用范围如下:网站数据: Mongo 非常适合实时的插入,更新与查询,并具备网站实时数据存储所需的复制及高度伸缩性。 **缓存:**由于性能很高, Mongo 也...
If this value is returned, the * request was placed on the conflict queue of the specified resource and a call to the * LockGrantNotification::notify callback should be expected with the resource whose lock * was requested. */ LOCK_WAITING, /** * The lock request waited, but timed out...
mongos> var it = db.test.find({'i': 1, "old_id": {$exists: 1}}) 遍历计数1:mongos> var count = 0;while(it.hasNext()){if (it.next()["X"].length==32)++count}print(count) 遍历计数2:mongos> var count = 0;while(it.hasNext()){var item = it.next(); if (item['X']...
{ // Any filter; here the check is if Prop1 does not exist { "q", new BsonDocument{ ["Prop1"] = new BsonDocument("$exists", false) }}, // set it to the value of Prop2 { "u", new BsonArray { new BsonDocument { ["$set"] = new BsonDocument("Prop1", "$Prop2") }}...
How can I insert a document if it does not exist while not updating existing document if it exists? let's say I have a document as follows: { "company":"test", "name":"nameVal" } I want to check whether the collection contains company test, if it doesn't exist I ...
文章背景：在VBA代码中，有时需要创建动态数组，然后对该动态数组进行操作。如果该数组为空，在使用一些...