SQL Interview Slip-ups:

 

                 SQL Interview Slip-ups:

 4 Costly Mistakes Candidates Make for FAANG Interviews 

Today, I’m sharing 4 common SQL mistakes candidates make when preparing for FAANG interviews (and how to avoid each one).

You’ll learn:

  • 4 high-impact mistakes that cost candidates offers
  • Simple actions you can take (in 10 minutes or less) to fix them

Let’s dive in:

Mistake #1: Memorizing Queries Instead of Understanding Patterns

A lot of candidates try to memorize SQL solutions.

Bad idea.

FAANG interviews don’t test memory — they test problem-solving patterns.

For example, instead of memorizing a ROW_NUMBER() solution, you should understand:

  • When to use window functions
  • How partitioning works
  • Why ordering matters

Because in the interview, the question will look different — even if the pattern is the same.

Think of it like learning chess openings vs understanding strategy. One scales. The other doesn’t.

Imagine this:
You walk into an interview, see a completely new problem… and still solve it confidently because you recognize the pattern.

That’s how offers happen.

3 ways to fix this:

  • After solving a problem, ask: “What pattern is this?” (ranking, aggregation, joins, etc.)
  • Rewrite the same query using a different method
  • Explain your solution out loud like you're teaching someone

Mistake #2: Ignoring Edge Cases

Most candidates write a query… and stop there.

Top candidates? They think like engineers.

They ask:

  • What if there are NULLs?
  • What if there are duplicates?
  • What if the data is missing?

For example:
A simple COUNT(*) vs COUNT(column) can completely change your answer if NULLs exist.

FAANG interviewers LOVE edge cases. It’s how they separate good from great.

Imagine this:
You finish your query and say:
"One thing I’d check is how this behaves with duplicate records..."

That one sentence can elevate your entire interview.

3 quick ways to improve:

  • Always test your query with NULLs and duplicates in mind
  • Add a final step: “What could break this?”
  • Practice explaining assumptions before writing code

Mistake #3: Poor Communication During Queries

SQL interviews aren’t just about writing queries.

They’re about thinking out loud.

Many candidates go silent while coding… and that’s a problem.

Interviewers want to understand:

  • Your approach
  • Your trade-offs
  • Your reasoning

Even if your query isn’t perfect, strong communication can still get you through.

Imagine this:
Instead of silently typing, you say:
"I’m thinking of using a window function here to rank results because..."

Now you’re not just a coder — you’re a collaborator.

3 ways to communicate better:

  • Start with a high-level approach before writing SQL
  • Narrate what you’re doing as you write queries
  • Summarize your solution at the end

Mistake #4: Practicing Only Easy Questions

This is the silent killer.

Many candidates stay in their comfort zone solving easy LeetCode-style SQL problems.

But FAANG interviews often include:

  • Multi-step queries
  • Joins + window functions combined
  • Business logic layered on top

If you don’t practice harder problems, you’ll freeze in the interview.

Imagine this:
You see a complex query with 3 joins and a ranking condition… and instead of panicking, you break it down step by step.

That’s what preparation looks like.

3 ways to level up:

  • Practice medium + hard SQL problems regularly
  • Break complex problems into smaller subqueries
  • Time yourself (30–40 minutes per problem)

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