Use the $nin operator to select documents where the field value isn't in the specified array or the field doesn't exist.
array. Thesemultikey indexesallow queries to select documents that contain arrays by matching on element or elements of the arrays. MongoDB automatically determines whether to create a multikey index if the indexed field contains an array value; you do not need to explicitly specify the multikey...
注意,这个和js中的array.find()不一样,js的find是返回第一个符合条件的属性和值,返回的是一个键值对对象 在mongo中这个条件会查询所有name属性值是韩振方的,然后返回,即便结果只有一个文档符合条件,也需要用[index]来调用里面的属性,味道有点像document.getElementByClassName()和document.querySelectorAll()。 `...
1, ""scanAndOrder"" : false, ""indexOnly"" : true, ""nYields"" : 0, ""nChunkSkips"" : 0, ""millis"" : 0, ""indexBounds"" : { ""gender"" : [ [ ""M"", ""M"" ] ], ""user_name"" : [ [ { ""$minElement"" : 1 }, { ""$maxElement"" : 1 } ] ] } }...
方法: MongoDB中的集合查询(获取一组文档中某个字段的不同值列表) 运用方法:DBCollection对象方法中的 distinct() 语句: 语句结构:distinct(key,[query]) key字符串,指定获取哪个字段的不同值;query:包含标准查询选项的对象,指定了要从哪个文档
Learn about the $map aggregation operator, which applies an expression to each item in an array and returns an array with the applied results.
arrayToObject是 concatArrays是 filter是 indexOfArray是 isArray是 objectToArray是 range是 reverseArray是 reduce是 size是 slice是 zip是 in是 变量运算符 展开表 命令支持 map是 let是 系统变量 展开表 命令支持 $$CLUSTERTIME是 $$CURRENT是 $$DESCEND是 ...
Array operators Command3.64.05.0Elastic cluster $arrayElemAt Yes Yes Yes Yes $arrayToObject Yes Yes Yes Yes $concatArrays Yes Yes Yes Yes $filter Yes Yes Yes Yes $first - - No No $in Yes Yes Yes Yes $indexOfArray Yes Yes Yes Yes $isArray Yes Yes Yes Yes $last - - ...
// Gets or sets a value by name. // // 参数: // name: // The name. // // 返回结果: // The value. public override BsonValue this[string name] { get; set; } // // 摘要: // Gets the value of an element or a default value if the element is not found. ...
Returning a matching array element "$slice" is helpful when you know the index of the element, but sometimes you want whichever array element matched your criteria. You can return the matching element with the $-operator. Given the blog example above, you could get Bob’s comment back with...