SQL inputselect u.id,u.name,o.total from users u inner join orders o on u.id=o.user_id where o.total>100 order by o.total desc; Formatted output Format SQLCopy outputClear Paste a query, then select Format SQL. An online SQL formatter turns dense SQL into clause-separated text…
These 100 SQL MCQs with answers cover the concepts that appear repeatedly in beginner assessments, from SELECT and filtering through joins, grouping, constraints, and set operations. Answer each question before opening its explanation, then use every miss to name the…
The Node.js crypto module can encrypt data that your application must later recover. AES-256-GCM gives you ciphertext plus an authentication tag, so a modified payload fails instead of returning data you should trust. The executed command below shows both the…
Node.js signs every response, stores session data, and saves user records as plain bytes. If anyone reads those bytes from a database dump or a log file, they read your data. The crypto module that ships with Node.js lets you…
JavaScript uses null and undefined for different kinds of missing data. Every example below ran with Node.js 26.7.0 to show where the values come from, how each operator treats them, and which value survives a JSON request. Null and undefined…
Build a secure random password generator in Node.js with crypto.randomInt(), configurable character groups, and a runnable test.
A JSON Web Token (JWT) API issues a short-lived token after your application has authenticated an account, then verifies it before a protected route runs. I ran JWT_SECRET=development-only-secret node test.mjs on Node v24.18.0 with express 5.2.1 and jsonwebtoken 9.0.3, and…
Choose bcrypt when your Node.js deployment can install native modules. Choose bcryptjs when a pure JavaScript dependency makes installation or deployment simpler. Both libraries use the bcrypt format, so each can verify a hash made by the other. bcrypt vs…
eval() evaluates a string as JavaScript source code. A direct call can read names in the surrounding scope, so the important question is where the string came from before you focus on its syntax. How eval() evaluates a string When…
Use this online password generator when you need a unique password that you can save in a password manager. It generates the value in your browser with the Web Crypto API, so the page does not send the password to…
