MySQL 8.0: Issues with Recursive CTEs and Temporary Tables in Complex Queries
I'm working with MySQL 8.0 and trying to implement a complex query that involves both recursive Common Table Expressions (CTEs) and temporary tables... The goal is to calculate hierarchical relationships from an employee table and store interim results in a temporary table for further analysis. However, I'm running into unexpected behavior where the recursive CTE seems to return incorrect results after inserting data into the temporary table. Here’s the setup: I have an `employees` table structured like this: ```sql CREATE TABLE employees ( id INT PRIMARY KEY, name VARCHAR(100), manager_id INT, FOREIGN KEY (manager_id) REFERENCES employees(id) ); ``` I populate it with some sample data: ```sql INSERT INTO employees (id, name, manager_id) VALUES (1, 'Alice', NULL), (2, 'Bob', 1), (3, 'Charlie', 1), (4, 'David', 2), (5, 'Eve', 2); ``` Next, I'm using a recursive CTE to get the hierarchy: ```sql WITH RECURSIVE employee_hierarchy AS ( SELECT id, name, manager_id FROM employees WHERE manager_id IS NULL UNION ALL SELECT e.id, e.name, e.manager_id FROM employees e INNER JOIN employee_hierarchy eh ON e.manager_id = eh.id ) SELECT * FROM employee_hierarchy; ``` This part works fine and returns the entire hierarchy. However, I then want to insert the results into a temporary table for further processing: ```sql CREATE TEMPORARY TABLE temp_hierarchy (id INT, name VARCHAR(100)); INSERT INTO temp_hierarchy (id, name) SELECT id, name FROM employee_hierarchy; ``` After executing the insert, I attempt to query the `temp_hierarchy` table, but I get an empty result set, even though the previous select statement returned rows. Additionally, if I try to run the recursive CTE again after the insert, it seems to ignore records that should still be there, providing inconsistent results. I've checked that the temporary table is being created successfully before the insert, and I'm aware that MySQL requires proper session handling for temporary tables. I also confirmed that no other queries are interfering with this context. Is there something about the order of operations or scope that I might be missing? Any insights into how to properly combine recursive CTEs with temporary tables in MySQL 8.0 would be greatly appreciated!