LDLakshay Dhoundiyalinlakshaydhoundiyal.hashnode.dev·4h ago · 8 min readWhy Do Banks Use Oracle Database? The Technology Behind Modern BankingYou open your banking app. You enter ₹10,000. You tap Send. A few seconds later: “Transaction Successful.” ✅ Simple, right? Not really. Behind that tiny confirmation message, several systems have alre20
APAbhinav Prakashinblog.iamabhinav.dev·9h ago · 19 min readHow to design a scalable DB SchemaI used to think database design was mostly about knowing SQL. You know: CREATE TABLE users (...); CREATE TABLE posts (...); Then add a few foreign keys, write some joins, and you're done. But after d00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 21 min readSQL Window Functions: How to Get the Top Row Per GroupBy the end of this page you can answer the question that stops most people the first week they write SQL: which row is the best one in each category. You will know OVER and PARTITION BY, the three ran00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 17 min readGROUP BY and HAVING: How to Summarize Rows Without Getting a Fake AnswerBy the end of this page you can write a summary query and know its answer is real. You will know exactly what GROUP BY does to your rows, which columns you are allowed to select afterwards and why, wh00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 20 min readSQL Foundations, Start to FinishBy the end of this page you can say, out loud and in your own words, what every core piece of SQL does. What a table and a row really are. The six clauses, and the order they actually run in, which is00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 16 min readSQL CTEs: How to Build a Query in Steps You Can CheckBy the end of this page you can take a question that needs four decisions and write it as four named steps, each one testable on its own. You will know the WITH syntax, how to stack one step on the ne00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 17 min readSQL Aliases: How to Read a Query Out LoudAfter this page you can read any query out loud and know what every name in it refers to. You will also name things the way a reviewer expects. That is most of what makes a query look like the work of00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 22 min readSQL JOINs: How to Join Two Tables Without Losing or Doubling RowsBy the end of this page you can predict, before you run it, how many rows any join will return. You will know all six join types and what each keeps. You will know the two ways a join goes wrong witho00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 8 min readCOUNT in SQL, Explained for BeginnersCOUNT looks like the simplest function in SQL, and it is the one that quietly trips up the most people in interviews and on the job. The confusion is almost always the same: COUNT(*), COUNT(column), a00
MNMichael Nocitoinmichaelnocito.hashnode.dev·1d ago · 12 min readThe SQL CASE Expression, Explained for BeginnersCASE is SQL's if/else. It is how you clean messy values, sort numbers into bands, build flags, and count several things in one query. This guide covers the whole of it. How CASE decides. Both forms of00
