---
title: "Why Does a SQL LEFT JOIN Return More Rows Than the Left Table?"  
description: "Why Does a SQL LEFT JOIN Return More Rows Than the Left Table?"  
author: "Aashish Khadka"  
published: 2026-10-17  
canonical: https://answers.mindstick.com/qa/117749/why-does-a-sql-left-join-return-more-rows-than-the-left-table  
category: "Mix Category"  
tags: ["SQL", "Databases", "programming"]  
reading_time: 1 minute  

---

# Why Does a SQL LEFT JOIN Return More Rows Than the Left Table?

I expected this query to return one row per customer, but customers with several orders show up multiple times. Is that just how a **[one-to-many relationship](https://www.mindstick.com/articles/1497/many-to-many-and-one-to-many-relationship-using-ef-code-first-approach)** behaves in a LEFT JOIN, or could the join condition be wrong?

```sql
SELECT
    customers.customer_id,
    customers.name,
    orders.order_id
FROM customers
LEFT JOIN orders
    ON orders.customer_id = customers.customer_id;

-- A customer with multiple matching orders appears once per order.
```

When you need one row per customer, how do you decide whether to aggregate the orders, filter them, or change the query? I’m also curious about a reliable way to spot which matches are increasing the **LEFT JOIN row counts**.


---

Original Source: https://answers.mindstick.com/qa/117749/why-does-a-sql-left-join-return-more-rows-than-the-left-table

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