Create 50 Unique PostgreSQL Interview Questions (from Junior to Senior level). Format as Markdown.

You will need to collect 50 Unique PostgreSQL Technical Interview Questions (from Junior to Senior devs levels) in Markdown format with full but succinct answer. Questions shall be both theoretical (when to use X vs Y and etc) and practical (What is wrong with that code and etc.). DON'T PROVIDE POSSIBLE ANSWERS LIKE OPTIONS, IT IS NOT A TEST, only right answer with explanation needed. Just one answer shall be provided with full detailed explanation that will be considered as a valid answer on a real interview. Questions may be sourced from StackOverflow, StackExchange, Reddit threads, Medium posts, Quora (less preferred) or from companies blogs or personal experience. Strongly NO COPY from crappy Indian QAS aggregators like "[login to view URL]", "geeksforgeeks", "w3school" and etc. . Every questions MUST contain Link to Answer source and Difficulty Level (Entry, Junior, Mid, Senior, Expert). QAS shall be created, formatted and shared via [login to view URL] Example of finished and accepted questions and answers: [login to view URL] To be chosen for this work: 1. Create an example document using [login to view URL] 2. Add three (3) Questions with answers, links to source and difficulty level for: Junior, Mid and Senior level 3. Share link with me in chat using [login to view URL] Don't waste your time - no example document shared, no response.