CTE with multiple references to the recursive table

[Oliver Demetz]

This query does work under postgres and I need something similar for mysql:

```
WITH RECURSIVE dependent(id) AS (
SELECT id FROM data_category WHERE id = :cat
UNION (
WITH parents AS ( SELECT * FROM dependent)
SELECT child_id AS id
FROM data_category_1 dc
INNER JOIN parents ON dc.id = parents.id
UNION
SELECT child_id AS id
FROM data_category_2 dc
INNER JOIN parents ON dc.id = parents.id
)
)
SELECT id from dependent
```
There are two problems:
1. I think the nested (WITH parents...) is a problem
2. I use this to only access the recursive part once, is this possible in any other way?