HIGHPerformancesmallSQL & Databases

Avoid N+1 queries (batch or join)

Fetch related data with a join or a single batched query instead of one query per row.

Why This Matters

Issuing one query per parent row multiplies round trips and degrades latency catastrophically as data grows.

Related Rules

Add Indexes for Frequent Queries

Performance

HIGH

Avoid SELECT * in Production

Performance

MEDIUM

Use Parameterized Queries

Security

CRITICAL

Normalize Data Appropriately

Architecture

MEDIUM

Catch this automatically on every PR

BeforeMerge scans your pull requests against this rule and dozens more. Get actionable feedback before code ships.

Join Waitlist Browse All Rules

Why this matters

Looping over results and querying inside the loop turns one request into N+1 round trips. The cost grows linearly with the data and dominates latency under load. Fetch everything in one join or one batched IN query.

// Bad: N+1 — one query per order
const orders = await db.query("SELECT * FROM orders");
for (const o of orders) {
  o.items = await db.query("SELECT * FROM items WHERE order_id = $1", [o.id]);
}

// Good: single join (or one IN-batched query)
const rows = await db.query(
  "SELECT o.*, i.* FROM orders o LEFT JOIN items i ON i.order_id = o.id"
);