WITH RECURSIVE category_tree AS ( SELECT id, name, parent_id, 0 AS level FROM categories WHERE parent_id IS NULL UNION ALL SELECT c.id, c.name, c.parent_id, ct.level + 1 FROM categories c JOIN category_tree ct ON c.parent_id = ct.id)SELECT * FROM category_tree; RECURSIVE报错语法错误

根据您提供的代码片段，出现语法错误的可能原因是在使用WITH RECURSIVE时，前面的查询子句中没有使用逗号分隔不同的SELECT语句，导致解析出错。您可以尝试将两个SELECT语句用逗号分隔开来，如下所示：

WITH RECURSIVE category_tree AS (
    SELECT id, name, parent_id, 0 AS level
    FROM categories
    WHERE parent_id IS NULL
    UNION ALL
    SELECT c.id, c.name, c.parent_id, ct.level + 1
    FROM categories c
    JOIN category_tree ct ON c.parent_id = ct.id
)
SELECT * FROM category_tree;

这应该可以解决语法错误问题。如果还有其他问题，请提供具体的错误信息，以便我更准确地帮助您解决问题。