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C++ || STL || standard template libraries

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                                       C++ STL  1.      Pair :  Syntax :      pair <int,char> p1;     it creates a pair {2,'c'} like this.           pair <int,int> p2;     it creates a pair {2,3} like this .  Basic Code :  #include <bits/stdc++.h> using namespace std; int main() {     // cout<<"hello world\n";     pair <int,int> p1 = {1,2};     cout<<p1.first<< " "<< p1.second<<endl;          pair <int, pair<int ,char>> p2 = {1,{2,'c'}};     cout<<p2.first<<" "<<p2.second.first<<" "<<p2.second.second<<endl;          pair <int,int> arr[] = {{2,3},{4,5},{6,7}};     cout...
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Percentage of users attending the contest || Leetcode solution || simple explanation ||💯💯💯💯✅✅✅🔥🔥🔥🔥

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                                1633 .   Percentage of Users Attended a Contest Problem:- To find the percentage of users attending contest from users and register table  Link for question :-  click here so we need to use group by contest_id then aggregation is performed on count(register.user_id) Approach select count ( * ) from users This will get the total count of the table in users is 3. count ( register . user_id ) At first group by is done on contest_id (multiple rows to single row) and aggregation is done on count(register.user_id) SQL Solution :-  # Write your MySQL query statement below select register . contest_id , round ( count ( register . user_id ) * 100 / ( select count ( * ) from users ) , 2 ) as percentage from users inner join register on users . user_id = register . user_id group by contest_id order by percentage desc , contest...
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Bank account summary II || Leetcode SQL query || Fully-Explained || 💯💯💯✅✅✅🔥🔥🔥

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                           1587 .   Bank Account Summary II 👇👇👇 Write an SQL query to report the name and balance of users with a balance higher than  10000 . The balance of an account is equal to the sum of the amounts of all transactions involving that account. Return the result table in  any order . The query result format is in the following example. Explanation: Alice's balance is (7000 + 7000 - 3000) = 11000. Bob's balance is 1000. Charlie's balance is (6000 + 6000 - 4000) = 8000. SQL Solution :- # Write your MySQL query statement below # select * select name , sum ( amount ) as balance from users inner join transactions on users . account = transactions . account group by name having balance > 10000 ; Full-Explanation :-  Appoach:    We need to find the name and balance of the tables.  balance is sum of amount Query: firstly, sel...
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