SQL Learning Outcomes

Where the Industry is Heading: Your Brains + Bots

🧠 + 🤖 Use AI Copilots

  • Engineers move 10x faster with GPT/Claude.
  • But firms aren't paying for glorified typists.
  • They need engineers who question and leverage AI outputs to deliver accurate logic faster.

🧠 Semantic Interviews

  • 50% of data interview questions focus on SQL logic.
  • Filter out the copy-pasters with whiteboard sessions: write logic, no AI, pure reasoning.
  • "Debug this query" - is it right or wrong? Expensive or cheap? How to fix?

☁️ Cloud Scale Reality

  • BigQuery, Snowflake, Redshift are everywhere.
  • Massively parallel and distributed execution across thousands of machines.
  • Optimize costs through smart design.

What You'll Do in CS145

🧠 Use Your Brain

  • Write SQL logic (on paper or whiteboard) without an IDE.
  • Use Debug Tables to trace semantics.

Prep for Whiteboard Interviews: Ace Test 1 on paper (50% SQL)

Example Anecdote 1:

  • Project 1: NULL values problem. Mismatches due to COUNT(rating), COUNT(*), and count(user_id).
  • Traced on paper: 50 NULL ratings. COUNT(column) skips NULLs, COUNT(*) counts all rows.

🤖 Experiment with LLMs

  • Explore subqueries, window functions, analysis.
  • Project 1: Experiment with what works; learn when AI misleads.

Prep for Interviews: "What's your AI workflow for data pipelines?"

Example Anecdote 2:

  • Project 2: Claude built my 3-level CTE in seconds. But level 2 referenced level 3 (doesn't exist yet). Also, its LEFT JOIN + COUNT(*) counted NULLs.
  • Fixed: reordered CTEs, used COUNT(t2.id).
  • Saved 30 mins writing, took 10 mins debugging.

☁️ Cloud Databases

  • Query gigabytes of data on BigQuery.
  • Understand parallel execution.
  • Optimize production queries for cost and speed.

Prep for Interviews: Create a data portfolio on BigQuery+Colab

Example Anecdote 3:

  • Project 1: Query kept timing out, cost $10.50 per run.
  • Checked execution plan: scanning 2.1TB before filtering. Moved date filter before JOIN - partition pruning kicked in.
  • Now 73GB, $0.37, runs in 12 seconds. Here's my colab on [topic X].

Project 1: Practice All Three Skills

Why these topics?

These are exactly what you'll use in summer internships, technical interviews, and your full-time roles.