Instant feedback on your SQL query quality
Every query you write in SQLizm gets a Bolton Score—a simple 1-10 rating that explains how well your SQL performs and why. No more fumbling in the darkness wondering if that JOIN is slowing things down or if you've accidentally created a Cartesian product. You'll understand exactly what's happening.
From 10 Boltons (perfect) to 1 Bolton (problematic)—here's what each score means
Your query uses indexes effectively and follows best practices. You understand exactly why it performs well. No more fumbling in the darkness.
Minor optimizations possible, but your query is solid. Small tweaks could make it even better.
Your query works, but there are performance concerns. Review our suggestions to improve it.
This query has serious performance problems. It might work on small datasets but will struggle at scale.
Stop! This query has critical issues like cross joins without conditions or massive Cartesian products. Refactor needed.
As you write your query, SQLizm analyzes the structure, table relationships, and execution plan in real-time.
Our intelligent heuristics check for common performance pitfalls: missing indexes, inefficient JOINs, SELECT *, table scans, and more.
Get your Bolton Score immediately with specific suggestions for improvement. Click on any issue to learn why it matters and how to fix it.
Each suggestion explains not just what to fix, but why it matters. No more wondering why a query is behaving badly—you'll understand the root cause.
Common query issues that affect your Bolton Score
JOINs or WHERE clauses on columns without indexes cause slow table scans.
Selecting all columns when you only need a few wastes bandwidth and memory.
Joins without conditions create Cartesian products—exponentially more rows than intended.
Querying large tables without WHERE clauses or indexes forces full table scans.
Nested subqueries that could be rewritten as JOINs often perform poorly.
Functions on indexed columns (e.g., WHERE UPPER(name) = 'JOHN') prevent index usage.
SELECT *
FROM users, orders
WHERE users.created_at > '2023-01-01'SELECT u.id, u.name, o.order_id, o.total
FROM users u
INNER JOIN orders o ON u.id = o.user_id
WHERE u.created_at > '2023-01-01'
AND u.created_at < '2024-01-01'