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This approach utilizes SQL LEFT JOIN to find all visits that do not have corresponding transactions and GROUP BY to count the occurrences.
Time Complexity: O(N + M), where N is the number of rows in the Visits table and M is the number of rows in the Transactions table.
Space Complexity: O(K), where K is the number of unique customer_id entries in the result set.
1// JavaScript using node-sqlite3
2const sqlite3 = require('sqlite3').verbose();
3
4let db = new sqlite3.Database('./your_database.db', (err) => {
5 if (err) {
6 console.error(err.message);
7 }
8 console.log('Connected to the SQlite database.');
9});
10
11let sql = `
12SELECT customer_id, COUNT(visit_id) AS count_no_trans
13FROM Visits
14LEFT JOIN Transactions ON Visits.visit_id = Transactions.visit_id
15WHERE Transactions.transaction_id IS NULL
16GROUP BY customer_id;`;
17
18// Execute SQL query
19let customerVisits = db.all(sql, [], (err, rows) => {
20 if (err) {
21 throw err;
22 }
23 rows.forEach((row) => {
24 console.log(`${row.customer_id} - ${row.count_no_trans}`);
25 });
26});
27
28db.close((err) => {
29 if (err) {
30 console.error(err.message);
31 }
32 console.log('Close the database connection.');
33});This JavaScript solution uses the sqlite3 library for Node.js to open a database connection, execute a query, and process the results. The query uses SQL LEFT JOIN and COUNT to list customers who visited but didn't make transactions.
This approach uses a subquery with NOT EXISTS to find all visits by customers that do not appear in the Transactions table.
Time Complexity: O(N * M), where N is the number of rows in the Visits table and M is the number of rows in the Transactions table.
Space Complexity: O(K), where K is the number of unique customer_id entries in the result set.
#include <iostream>
#include <string>
#include <sqlite3.h>
void executeSQL(const std::string &query) {
sqlite3 *db;
char *zErrMsg = nullptr;
int rc;
rc = sqlite3_open("your_database.db", &db);
if(rc) {
std::cerr << "Can't open database: " << sqlite3_errmsg(db) << std::endl;
return;
}
rc = sqlite3_exec(db, query.c_str(), callback, 0, &zErrMsg);
if(rc != SQLITE_OK) {
std::cerr << "SQL error: " << zErrMsg << std::endl;
sqlite3_free(zErrMsg);
}
sqlite3_close(db);
}
int main() {
std::string query = "SELECT customer_id, COUNT(visit_id) AS count_no_trans FROM Visits WHERE NOT EXISTS (SELECT * FROM Transactions WHERE Visits.visit_id = Transactions.visit_id) GROUP BY customer_id;";
executeSQL(query);
return 0;
}
// Note: Make sure to implement the callback function and handle the database initialization and cleanup properly. The query provided is SQL and should be run on a SQL-compliant database like SQLite3.In C++ using a SQLite3 database, the code opens a connection, runs a query embedding a subquery with the NOT EXISTS clause, and outputs the results. This strategy efficiently identifies visits without transactions, utilizing SQL capabilities within the C++ environment.