7 SQL Skills Every Data Job Asks For (And How to Prove Them)

Read through ten data job postings and a pattern jumps out: the same SQL skills appear again and again. Master these seven and you'll meet the bar for the vast majority of analyst and data roles.

The seven skills that show up everywhere

1. Filtering and sorting — WHERE, ORDER BY, LIMIT, and the operators (IN, BETWEEN, LIKE) that make them precise.
2. Joins — combining tables with INNER and LEFT JOIN is the single most tested skill in interviews.
3. Aggregation — GROUP BY with COUNT, SUM, and AVG to turn rows into insight.
4. Filtering groups — HAVING, and knowing exactly why it differs from WHERE.
5. Subqueries and CTEs — breaking a hard question into readable steps with WITH.
6. Window functions — ROW_NUMBER, RANK, and running totals; the skill that separates juniors from mid-level.
7. Conditional logic — CASE expressions for bucketing and pivoting data.

SELECT
  customer_id,
  SUM(total) AS lifetime_value,
  CASE
    WHEN SUM(total) > 1000 THEN 'VIP'
    WHEN SUM(total) > 250  THEN 'Regular'
    ELSE 'New'
  END AS segment
FROM orders
GROUP BY customer_id;

The mistake most candidates make

They read about these skills instead of writing them. You can recognize a window function on a slide and still freeze when an interviewer asks you to produce one. Recognition is not the same as recall under pressure.

How to actually prove them

The only reliable proof is having written real queries against real data — and a credential that says so. SQLCertified covers all seven of these skills with interactive lessons and live, in-browser challenges, then backs them with a verifiable certification. Walk into your next interview knowing you've already solved the exact kinds of problems they're about to ask. Start building that proof today.