$size to find a range of sizes (for example: arrays with more than 1 element). If you need to query for a range, create an extra size 7)$exists $exists用来判断一个元素是否存在: 如: db.things.find( { a : { $exists : true } } ); // 如果存在元素a,就返回 db.things.find( {...
{ $pullAll: { <field1>: [ <value1>, <value2> ... ], ... } } $pull 符合条件的值将被删除 { $pull: { <field1>: <value|condition>, <field2>: <value|condition>, ... } } $pushAll 向数组中追加多个指定值 { $pushAll: { <field>: [ <value1>, <value2>, ... ] } }...
The following aggregation uses the$regexMatchto check if thecommentfield contains an email address with@mongodb.comand categorize the feedback asEmployeeorExternal. db.feedback.aggregate([ {$addFields:{ "category":{$cond:{if:{$regexMatch:{input:"$comment",regex:/[a-z0-9_.+-]+@mongodb.co...
> db.help() DB methods: db.adminCommand(nameOrDocument) - switches to 'admin' db, and runs command [just calls db.runCommand(...)] db.aggregate([pipeline], {options}) - performs a collectionless aggregation on this database; returns a cursor db.auth(username, password) db.cloneDatabase...
db.mycol.aggregate([{$group : {_id : "$by_user", url : {$addToSet : "$url"}}}]) $first 根据资源文档的排序获取第一个文档数据。 db.mycol.aggregate([{$group : {_id : "$by_user", first_url : {$first : "$url"}}}]) $last 根据资源文档的排序获取最后一个文档数据 db.mycol....
Check your driver documentation to see when your driver added support. $indexStats Starting in MongoDB 4.4 (also available starting in 4.2.4), $indexStats includes the following fields in its output: Field Description shard Name of the shard, if applicable. spec Index specification document ...
db.aggregate([pipeline],{options})-对该数据库执行无集合聚合;返回一个指针(目前不知道在哪使用) db.auth(username,password)(目前不知道在哪使用) db.cloneDatabase(fromhost)-will onlyfunctionwithMongoDB4.0and below db.commandHelp(name)returns the helpforthe command ...
通过引用方式 aggregate聚合框架中的 $lookup操作符 来进行关联查询 例如:users集合 和 user_hobby集合 将这两个集合进行关联查询 代码语言:javascript 复制 // users集合关联user_hobby集合 db.users.aggregate([ { $lookup: { from: "user_hobby", //目标关联集合 localField: "hobbys", //当前集合要关联的字...
aggregate Yes Yes Yes Yes count Yes Yes Yes Yes distinct Yes Yes Yes Yes mapReduce No No No No Authentication Command3.64.05.0Elastic cluster authenticate Yes Yes Yes Yes logout Yes Yes Yes Yes Diagnostic commands Command3.64.05.0Elastic cluster buildInfo Yes Yes Yes Yes collStats Ye...
MongoDB is a popular schemaless, in-memory database with a wide range of applications. As an important part of MongoDB, MongoDB Aggregate is mainly...