You can"t specify target table for update in FROM clause

📝 Tech Blog: Can't specify target table for update in FROM clause

💡 Introduction: Have you ever encountered the error "You can't specify target table for update in FROM clause" while running a MySQL update query? It can be frustrating, especially when you're not sure how to fix it. In this blog post, we will address this common issue and provide you with easy solutions to resolve it. So, let's dive in!

🔍 Understanding the Problem: The error occurs when you try to update a table based on a subquery, and the table you want to update is also present in the subquery. In your case, you received the error while trying to run the following update query:

UPDATE pers P 
SET P.gehalt = P.gehalt * 1.05 
WHERE (P.chefID IS NOT NULL 
OR gehalt < 
(SELECT (
    SELECT MAX(gehalt * 1.05) 
    FROM pers MA 
    WHERE MA.chefID = MA.chefID) 
    AS _pers
))

💡 Solution: To fix this issue, you have two possible solutions:

1️⃣ Use a Temporary Table: You can create a temporary table to store the results of the subquery, and then join it with the main table in the update query. This will allow you to update the table without encountering the error. Here's how you can modify your query:

CREATE TEMPORARY TABLE temp_table AS
(SELECT MAX(gehalt * 1.05) AS _pers FROM pers);

UPDATE pers P
JOIN temp_table T ON P.chefID = P.chefID
SET P.gehalt = P.gehalt * 1.05
WHERE P.chefID IS NOT NULL OR P.gehalt < T._pers;

2️⃣ Use a Derived Table: Another solution is to use a derived table, which involves creating a subquery within the FROM clause and giving it an alias. With this approach, you can perform the update without encountering the error. Here's an example:

UPDATE pers P
SET P.gehalt = P.gehalt * 1.05
WHERE P.chefID IS NOT NULL OR P.gehalt <
    (SELECT _pers
    FROM
        (SELECT MAX(gehalt * 1.05) AS _pers
        FROM pers MA
        WHERE MA.chefID = MA.chefID) AS temp_table);

📣 Conclusion: Now that you know how to fix the "You can't specify target table for update in FROM clause" error, you can confidently update your MySQL tables using subqueries. Remember to choose either the temporary table or derived table approach, depending on your preference and the complexity of the query.

We hope this blog post helped you solve this common MySQL issue. If you have any questions or other tech-related topics you'd like us to cover, let us know in the comments below.

🙌 Engagement Call-to-Action: Have you ever faced any MySQL query errors? How did you resolve them? Share your experiences in the comments section below. Let's learn and troubleshoot together! 🚀