Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
Know what data you need but struggling with SQL syntax? AI writes the query for you. The Prompt: Write SQL query for this: Database: Ecommerce Tables: Users (id, name, email), Orders (id, user_id, total, created_at) I need: Top 10 customers by total order value in last 30 days Also explain what each part does. AI […]
Writing complex analytical queries with self-joins and subqueries? Window functions perform calculations across rows without grouping. Common Window Function Patterns: — Basic structure SELECT column1, column2, WINDOW_FUNCTION() OVER ( PARTITION BY partition_column ORDER BY sort_column ROWS/RANGE BETWEEN frame_start AND frame_end ) AS calculated_column FROM table_name; — Available functions: — Ranking: ROW_NUMBER(), RANK(), DENSE_RANK(), NTILE() — […]
Using .Count() > 0 to check if a collection has items? You’re forcing LINQ to enumerate the entire collection just to answer a yes/no question. The Performance Killer: var users = dbContext.Users.Where(u => u.IsActive); // BAD: Counts ALL active users first if (users.Count() > 0) { Console.WriteLine(“We have active users”); } // Database query generated: […]