cartesian-product

as definition: The cartesian product of two sets is the set of all possible pairs of these sets, so {A,B} x {a,b} = {(A,a),(A,b),(B,a),(B,b)}. Now i want to insert such a cartesian product into a database table (each pair as a row). It is intended to fill the table with default values for each pair, so the data, i.e. the two sets, are not present in the database at this point. Any idea how to achieve this with postgresql? EDIT : With the help of Grzegorz Szpetkowski's answer I was able to produce a query that does what I want to achieve, but it really isn't the prettiest one. Suppose I want to

I have an object of the following form (simplified test case below) var test = { shirts: { sizes: ['large', 'medium'] ,colors:['red', 'blue'] } , trousers: { type: ['formal', 'casual'] , pattern: ['plaid', 'stripes'] } }; I want to generate a cartesian product of the properties so that the output is an array of the following form: // desired output [ {shirts:{sizes:'large', color:'red'}, trousers:{type:'formal', pattern:'plaid'}} ,{shirts:{sizes:'large', color:'red'}, trousers:{type:'formal', pattern:'stripes'}} ,{shirts:{sizes:'large', color:'red'}, trousers:{type:'casual', pattern:'plaid'}}

How can I implement a function using Java 8 to take some number of streams, and produce a stream in which each element is a list consisting of one member of the Cartesian product of the streams? I've looked at this question -- that question uses an aggregator that is a BinaryOperator (taking two items of like type and producing an item of the same type). I'd like the items in the end result to be List s rather than the types of the elements in the input streams. Concretely, supposing my desired function is called product , the following: Stream<List<String>> result = product( Stream.of("A", "B

let's say I have two lists: a = list(1,2,3) b = list(4,5,6) So I can have 9 pairs of these list members: (1,4) (1,5) (1,6) (2,4) (2,5) (2,6) (3,4) (3,5) (3,6) Now, given two list members like above, can I find out the pair's index? Like (1,4) from above would be the 1st pair. And to complete the answer and stay in the example: import itertools a = [1, 2, 3] b = [4, 5, 6] c = list(itertools.product(a, b)) idx = c.index((1,4)) But this will be the zero-based list index, so 0 instead of 1. One way to do this: Find the first element of the pair your are looking for in the first list: p = (1, 4) i

SELECT user_id, SUM(COALESCE(point_points, 0)) AS total_points, SUM( CASE WHEN point_date > '$this_month' THEN point_points ELSE 0 END) AS month_points, COUNT(DISTINCT c_id) AS num_comments, COUNT(DISTINCT rant_id) AS live_submissions FROM users LEFT JOIN points ON users.user_id = points.point_userid LEFT JOIN comments ON ( c_userid = user_id ) LEFT JOIN rants ON ( rant_poster = user_id AND rant_status = 1 ) WHERE user_id = $id GROUP BY user_id Basically live_submissions and num_comments variable display proper results, while the total_points and month_points display a product of month_points

Let's say I have 2 groups of numbers: {1, 2, 3}, {4, 5} I'd like to create an algorithm (in Java) that outputs the following 6 combinations: 1,4 1,5 2,4 2,5 3,4 3,5 There can be an arbitrary number of groups and an arbitrary number of members within each group. So in the above example, there are 2 groups with the first group having 3 members and the second group having 2 members. Another example is the following (3 groups, 3 members in first groups and 2 members in second and third groups): {1, 2, 3}, {4, 5}, {6, 7} Which would yield the following 12 combinations: 1,4,6 1,4,7 1,5,6 1,5,7 2,4,6