Úprava SQL dotazu pro návrat stromové struktury dat

Dobrý den,
mám dotaz

SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4

FROM category AS t1

LEFT JOIN category AS t2 ON t2.parent = t1.category_id

LEFT JOIN category AS t3 ON t3.parent = t2.category_id

LEFT JOIN category AS t4 ON t4.parent = t3.category_id

WHERE t1.name = 'ELECTRONICS'

který vrací

+-------------+----------------------+--------------+-------+

| lev1        | lev2                 | lev3         | lev4  |

+-------------+----------------------+--------------+-------+

| ELECTRONICS | TELEVISIONS          | TUBE         | NULL  |

| ELECTRONICS | TELEVISIONS          | LCD          | NULL  |

| ELECTRONICS | TELEVISIONS          | PLASMA       | NULL  |

| ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS  | FLASH |

| ELECTRONICS | PORTABLE ELECTRONICS | CD PLAYERS   | NULL  |

| ELECTRONICS | PORTABLE ELECTRONICS | 2 WAY RADIOS | NULL  |

+-------------+----------------------+--------------+-------+

Napadá vás, jak ho jednoduše upravit, aby vracel

+-------------+----------------------+--------------+-------+

| lev1        | lev2                 | lev3         | lev4  |

+-------------+----------------------+--------------+-------+

| ELECTRONICS | NULL                  | NULL         | NULL  |

| ELECTRONICS | TELEVISIONS          | NULL         | NULL  |

| ELECTRONICS | TELEVISIONS          | TUBE         | NULL  |

| ELECTRONICS | TELEVISIONS          | LCD          | NULL  |

| ELECTRONICS | TELEVISIONS          | PLASMA       | NULL  |

| ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS  | FLASH |

| ELECTRONICS | PORTABLE ELECTRONICS | CD PLAYERS   | NULL  |

| ELECTRONICS | PORTABLE ELECTRONICS | 2 WAY RADIOS | NULL  |

+-------------+----------------------+--------------+-------+

tedy i sloupce jako ELECTRONICS s hodnotami NULL v lev2, lev3, lev4 ap.?
Řešit to jde více dotazy, ale chtěl bych nějak upravit ten předchozí dotaz a večer už mi to nemyslí:)

Napadlo mě jen takové řešení:

SELECT CONCAT_WS( ",", t2.name, t3.name, t4.name ) AS path, t4.id as id

FROM category AS t1, category AS t2, category AS t3, category AS t4

WHERE t2.parent = t1.id

AND t3.parent = t2.id

AND t4.parent = t3.id

AND t1.name = "eshop"

UNION 

SELECT CONCAT_WS( ",", t2.name, t3.name ) AS path, t3.id as id

FROM category AS t1, category AS t2, category AS t3 

WHERE t2.parent = t1.id

AND t3.parent = t2.id

AND t1.name = "eshop"

UNION 

SELECT CONCAT_WS( ",", t2.name) AS path, t2.id as id 

FROM category AS t1, category AS t2

WHERE t2.parent = t1.id

AND t1.name = "eshop"

Tohle ale bude pomalé:/