---
title: "Why Do SQL Joins Create Duplicate Rows in My Results?"  
description: "Why Do SQL Joins Create Duplicate Rows in My Results?"  
author: "Arnaud Simon"  
published: 2026-10-21  
canonical: https://answers.mindstick.com/qa/118005/why-do-sql-joins-create-duplicate-rows-in-my-results  
category: "Mix Category"  
tags: ["SQL", "database design", "Query Debugging"]  
reading_time: 1 minute  

---

# Why Do SQL Joins Create Duplicate Rows in My Results?

I’m joining a customers table to an orders table, and the result has several copies of each customer. The customer IDs are unique in the first table, so I expected one row per customer.

Is this usually because one customer can have multiple matching orders, or can the join condition itself accidentally multiply rows? I’d also like to know what you check first when debugging **duplicate rows after a join**, especially when the query has more than two tables.


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Original Source: https://answers.mindstick.com/qa/118005/why-do-sql-joins-create-duplicate-rows-in-my-results

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