count

问题 db.foos { bar: ObjectId('123') } db.bars { _id: ObjectId('123') type: 'wine' } How can I in the simplest way find the number of foo-documents that refers to a bar-document of type 'wine'? Hopefully one that scales to perform fairly well even if the collections should contain a very large number of documents. 回答1: Try this aggregation framework query: db.foos.aggregate([ {$lookup: { from: "bars", localField: "_id", foreignField: "_id", as: "docs" } }, {$unwind: "$docs"}, {$match: {"docs.type":

问题 I am using visual basic and I want to count all the files that exist in a folder and in its subfolders.. I tried this : Dim counter = My.Computer.FileSystem.GetFiles("C:\Folder") MsgBox("number of files is " & CStr(counter.Count)) but it only counts files in the C:\Folder and not in C:\Folder\Sub-Folder\AnotherSubFolder What should I do? Thank's for help! 回答1: Use Directory.GetFiles() as defined here: https://msdn.microsoft.com/en-us/library/ms143316(v=vs.110).aspx So you'd just use Dim

问题 Let's say you have a search form, with multiple select fields, let's say a user selects from a dropdown an option, but before he submits the data I need to display the count of the rows in the database . So let's say the site has at least 300k(300.000) visitors a day, and a user selects options from the form at least 40 times a visit, that would mean 12M ajax requests + 12M count queries on the database, which seems a bit too much . The question is how can one implement a fast count (using

问题 Below is a couple of rows of some test data I am using. I am wanting to count the frequency of all the characters in the ICD10Code column which are separated by columns. From the segment of code below, I used group_by because every "PatientId" value had duplicates in that column but had unique values in other columns. How can I go about counting the frequency of all character values? PatientId ReferralSource NextAppt Age InsuranceName ICD10Code 1584 St Francis Y 34 SLIDING FEE SCHEDULE M5136,

问题 Im trying to Add a few methods to the Javascript String Object. one of the main methods im trying to add is a substring count function String.prototype.substring_count = function(delimiter){ return {THIS IS WHAT I NEED THE STRING FOR}.split(delimiter).length; } Where do you access the string in the String object? 回答1: Use this . In the documentation, it is mentioned If the method is on an object's prototype chain, this refers to the object the method was called on in this case, the string

问题 I would like to count how many times is every string in array and sort them by number of times they exist in array I have this code now hlasy.sort(); var zaciatok = null; var pocet = 0; for (var i = 0; i < hlasy.length; i++) { if (hlasy[i] != zaciatok) { if (pocet > 0) { console.log(zaciatok + ' má ' + pocet + ' hlasov'); } zaciatok = hlasy[i]; pocet = 1; } else { pocet++; } } if (pocet > 0) { console.log(zaciatok + ' má ' + pocet + ' Hlasov'); } it works, but it outputs strings from array

问题 I have a workbook with multiple sheets. On sheet1 I would like to count the number of times person in column A has a particular entry in Column C that meets criteria of column D = Content but only count if column B is a unique value. Using the below formula I can do everything except only counting unique numbers in Column B. I enter this formula in Sheet2 C2 then pull across to I2 then pull down to 6 in each column. =IF(COUNTIFS(Sheet1!$A$2:$A$150,Sheet2!$B2,Sheet1!$C$2:$C$150,Sheet2!C$1

问题 I have a workbook with multiple sheets. On sheet1 I would like to count the number of times person in column A has a particular entry in Column C that meets criteria of column D = Content but only count if column B is a unique value. Using the below formula I can do everything except only counting unique numbers in Column B. I enter this formula in Sheet2 C2 then pull across to I2 then pull down to 6 in each column. =IF(COUNTIFS(Sheet1!$A$2:$A$150,Sheet2!$B2,Sheet1!$C$2:$C$150,Sheet2!C$1

问题 I got stuck on SQL subquery selection. Right now, I have a table products: id | name | description ----+-------+---------------------- 6 | 123 | this is a + | | girl. 7 | 124 | this is a + | | girl. 8 | 125 | this is a + | | girl. 9 | 126 | this is a + | | girl. 10 | 127 | this is a + | | girl. 11 | 127 | this is a + | | girl. Isn't this? 12 | 345 | this is a cute slair 13 | ggg | this is a + | | girl 14 | shout | this is a monster 15 | haha | they are cute 16 | 123 | this is cute What I want

问题 I have a database that stores twitter data: Create Table tweet( ID BIGINT UNIQUE, user_ID BIGINT, created_at TIMESTAMPTZ, tweet TEXT; I'm trying to write a query that goes through the words in tweet for all rows gets the frequency of each word, and returns the top ten most frequent words along with the words' ranking over each date. Example: ("word1":[1,20,22,23,24,25,26,27,28,29,30,29,28,27,26,25,26,27,28,29,30,29,28,29,28,27,28,29,30,30,...], 'word2' [...]) My current query gets the top ten