官方的说明、Demo地址:https://www.mongodb.com/docs/manual/tutorial/query-array-of-documents/ 1.2 使用$elemMatch操作符查询,本文侧重该方式。 官方说明:The$elemMatchoperator matches documents that contain an array field with at least one element that matches all the specified query criteria. 就是说$...
官方的说明、Demo地址:https://www.mongodb.com/docs/manual/tutorial/query-array-of-documents/ 1.2 使用$elemMatch操作符查询,本文侧重该方式。 官方说明:The$elemMatchoperator matches documents that contain an array field with at least one element that matches all the specified query criteria. 就是说$...
You cannot use $size to find a range of sizes (for example: arrays with more than 1 element). If you need to query for a range, create an extra size field that you increment when you add elements. 7)$exists $exists用来判断一个元素是否存在: 如: db.things.find( { a : { $exists ...
官网上说不能用来匹配一个范围内的元素,如果想找$size<5之类的,他们建议创建一个字段来保存元素的数量。 You cannot use $size to find a range of sizes (for example: arrays with more than 1 element). If you need to query for a range, create an extra size field that you increment when you ...
Object 6. Array 7. BinData 8. ObjectId 9. Boolean 10. Date 11. Timestamp 12. Regular Expression 13. MaxKey (internal type) 在这个限制下, 就只需要对比同种类型的大小了,BSON 的基本比较流程如下:先比较类型,如果类型一样才使用 BSONElement::compareElements 比较值。
You cannot use $size to find a range of sizes (for example: arrays with more than 1 element). If you need to query for a range, create an extra size field that you increment when you add elements. 7)$exists $exists用来判断一个元素是否存在: 如: db.things.find( { a : { $exists...
Returns the first element in an array. $function Defines a custom aggregation expression. $last Returns the last element in an array. $isNumber Returns boolean true if the specified expression resolves to an integer, decimal, double, or long.Returns boolean false if the expression resolves to an...
$[element]" : 100 } }, { arrayFilters: [ { "element": { $gte: 100 } } ] } ) # 结果 更新单个文档 { "_id" : 1, "grades" : [ 95, 92, 90 ] } { "_id" : 2, "grades" : [ 98, 100, 100 ] } # 修改 { "_id" : 3, "grades" : [ 95, 110, 100 ] } ##准备...
If your query patterns require accessing individual array elements, use a multi-key index. MongoDB creates an index key for each element in the array and can be constructed over arrays that hold both scalar values and nested documents. Avoid Regular Expressions That Are Not Left Anchored or Roo...
To specify conditions on the elements in the array field, usequery operatorsin thequery filter document: { <array field>: { <operator1>: <value1>, ... } } For example, the following operation queries for all documents where the arraydim_cmcontains at least one element whose value is gr...