PostgreSQL delete with inner join

🚀 PostgreSQL Delete with Inner Join: Easy Solutions for Common Issues

Are you tired of struggling with the syntax error when trying to delete records using inner join in PostgreSQL? Don't worry, you're not alone! Many users encounter a similar problem when attempting to delete records from multiple tables based on a specific condition. In this blog post, we will walk you through the common issues and provide easy solutions to help you overcome this obstacle. So, let's dive right in! 💪

Understanding the Problem

Let's start by examining the original query that resulted in the syntax error:

DELETE B.* 
FROM   m_productprice B  
       INNER JOIN m_product C ON B.m_product_id = C.m_product_id 
WHERE  C.upc = '7094' AND B.m_pricelist_version_id = '1000020';

The error message you encountered was:

ERROR:  syntax error at or near "B"
LINE 1: DELETE B.* from m_productprice B  INNER JOIN m_product C ON ...

Analyzing the Error

The syntax error occurs because PostgreSQL doesn't support using the DELETE statement directly on table aliases. In this case, B is an alias for the m_productprice table. PostgreSQL only allows you to delete records from a single table using the DELETE statement, but fear not! We have some creative workarounds for you. 😎

Easy Solutions

Solution 1: Using Subquery

You can achieve the desired result by using a subquery. Instead of directly deleting from the m_productprice table, you can use a subquery to select the primary keys of the records you want to delete. Here's how you can modify your query:

DELETE FROM m_productprice
WHERE  m_productprice_id IN (
   SELECT B.m_productprice_id
   FROM   m_productprice B
          INNER JOIN m_product C ON B.m_product_id = C.m_product_id
   WHERE  C.upc = '7094' AND B.m_pricelist_version_id = '1000020'
);

In this solution, we select the m_productprice_id values from the subquery and delete the corresponding records from the m_productprice table.

Solution 2: Using a Common Table Expression (CTE)

Another way to tackle this issue is by using a Common Table Expression (CTE). A CTE allows you to define a temporary result set that you can reference later within the query. Here's how you can rewrite your query using a CTE:

WITH deleted_rows AS (
   SELECT B.m_productprice_id
   FROM   m_productprice B
          INNER JOIN m_product C ON B.m_product_id = C.m_product_id
   WHERE  C.upc = '7094' AND B.m_pricelist_version_id = '1000020'
)
DELETE FROM m_productprice
WHERE  m_productprice_id IN (SELECT m_productprice_id FROM deleted_rows);

This approach involves creating a CTE named deleted_rows, which selects the primary keys of the records you want to delete. Then, you delete the corresponding records from the m_productprice table using the DELETE statement.

📣 Your Turn to Engage

Now that you have two easy solutions to tackle the "delete with inner join" issue in PostgreSQL, it's time for you to put them into action. Try incorporating one of these methods into your SQL query and see the magic happen!

Have you encountered any other PostgreSQL challenges? Let us know in the comments below, and we'll be more than happy to help you find a solution. Let's make PostgreSQL querying a breeze for everyone! 🌈

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