distinct-values

I am trying to get the distinct values from a field in MongoDB. I am having real trouble with the Syntax. Using mongoshell it's relatively easy to do, this is the query I run: db.cmstest.distinct("categories") This query returns an array of strings with all the distinct values. Now I am trying to get the syntax right using the latest official MongoDB Drivers, but not to much success. This is my code, which is unsuccessful: var categoriesList = await blogContext.Articles.DistinctAsync<List<string>>("categories", ""); Mind you categories is a List<string> . Could anyone help shed some light? I

How can one get the distinct (distinct based on two property) list from a list of objects. for example let there are list of objects with property name and price. Now how can I get a list with distinct name or price. suppose list<xyz> l1 = getlist(); // getlist will return the list. Now let l1 has the following properties(name, price) :- n1, p1 n1, p2 n2, p1 n2, p3 Now after the filter the list should be- n1, p1 n2, p3 I tried solving like this - public List<xyz> getFilteredList(List<xyz> l1) { return l1 .stream() .filter(distinctByKey(xyz::getName)) .filter(distinctByKey(xyz::getPrice))

How to create a list of unique/distinct objects (no duplicates) in Java? Right now I am using HashMap<String, Integer> to do this as the key is overwritten and hence at the end we can get HashMap.getKeySet() which would be unique. But I am sure there should be a better way to do this as the value part is wasted here. Frank You can use a Set implementation: Some info from the JAVADoc: A collection that contains no duplicate elements . More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2), and at most one null element. As implied by its name, this interface models the

I have a mysql table that looks like this: 1 value1 value2 3534 2 value1 value1 8456 3 value1 value2 3566 4 value1 value3 7345 5 value2 value3 6734 I need a query to select all the rows with distinct column 2 and 3, for example the output I want for this example will look like this: 1 value1 value2 3534 2 value1 value1 8456 4 value1 value3 7345 5 value2 value3 6734 i've found a few samples on how to do it but they all select distinct on each column individually. Assuming that the first column is unique, you can do this: SELECT id, col2, col3, col4 FROM yourtable WHERE id IN ( SELECT MIN(id)

Basically, I would like help designing an algorithm that takes a given number, and returns a random number that is unrelated to the first number. The stipulations being that a) the given output number will always be the same for a similar input number, and b) within a certain range (ex. 1-100), all output numbers are distinct. ie., no two different input numbers under 100 will give the same output number. I know it's easy to do by creating an ordered list of numbers, shuffling them randomly, and then returning the input's index. But I want to know if it can be done without any caching at all.