(Note the extra $addFields stage as opposed to setting the value in the project as if you set the field value to 1 there, it regards this as a projection inclusion and does not actually set to 1, there must be a better way of doing this.) ...
db.collection.find({ "field" : { $gt: value1, $lt: value2 } } ); // value1 < field < value 2) 不等于 $ne 例子: db.things.find( { x : { $ne : 3 } } ); 3) in 和 not in ($in $nin) 语法: db.collection.find( { "field" : { $in : array } } ); 例子: db.t...
constquery={arrayField:{$elemMatch:{$exists:true}}};// 在这里编写步骤 4 的代码 1. 2. 3. 步骤4: 执行查询 然后,我们需要执行查询。使用find()方法可以实现这一步骤: collection.find(query).toArray(function(err,result){if(err)throwerr;// 在这里编写步骤 5 的代码}); 1. 2. 3. 4. 5. ...
使用$indexOfCP检查子字符串中是否存在matchingWord。如果matchingWord不在子字符串中，则将返回-1.$map此结果从matchingWords数组返回到布尔数组。使用$anyElementTrue检查搜索字符串中的任何单词。
('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(); }); })...
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...
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...
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...
use the $where and pass the this.field_name.length which return the size of array field and check it by comparing with number. if any array have any value than array size must be at least 1. so all the array field have length more than one, it means it have some data in that arr...
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 ...