Spotting & Fixing N+1 Queries

Problem

An ORM is issuing 1 query for the orders list and then 1 query *per order* to fetch the customer name (1+N). Identify the anti-pattern and rewrite it as a single SQL.

Input

Conceptual + SQL.

Output

Single JOIN query

Constraints

—

Sample input

—

Sample output

N+1 is fixed by JOINing once.

Explanation

The ORM is lazy-loading customer per row. A single JOIN replaces N+1 round-trips.

optimisationanti-patternjoins@Shopify

Visible test cases

in: explain

out: ok

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sql

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