Technology & Coding

SQL For Absolute Beginners

Write real SQL queries that filter, sort, group, and join data from a database with confidence.

This course is for members

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What you will learn about SQL for Absolute Beginners

The 7-day sprint
  1. Tables, Rows, And SELECT. A database stores data in tables of rows and columns, and SELECT is how you ask for some of those columns back.
  2. Filtering With WHERE. WHERE keeps only the rows that make a condition true, so you get answers instead of whole tables.
  3. Sorting, Limiting, And Distinct. ORDER BY controls the order of your results, LIMIT trims how many you see, and DISTINCT collapses duplicates.
  4. Aggregates And GROUP BY. Aggregate functions squash many rows into one number, and GROUP BY does that once per category.
  5. Joining Two Tables. A JOIN stitches rows from two tables together by matching a key value they share.
  6. Changing Data Safely. INSERT adds rows, UPDATE changes them, DELETE removes them, and each one needs a WHERE clause or a plan.
  7. Building A Real Query From Scratch. Every serious query is assembled in a fixed logical order, and knowing that order lets you write it without guessing.
The 80/20: the 6 concepts that matter most
  • The Table Is The Only Data Structure
  • WHERE Thinks One Row At A Time
  • Joins Match On Keys, And The Match Rate Decides Your Row Count
  • GROUP BY Is Just Bucketing Then Summarizing
  • NULL Means Unknown, Not Zero Or Empty
  • Write Destructive Statements As SELECTs First
The core idea, explained like you are 5

A SQL query is a written description of the rows you want, and the database figures out how to fetch them.

Then the quiz and the ladder

10 questions that correct you when you are wrong, and beginner, intermediate, advanced levels, each with a practical exercise.