我的查询使用了5个表：
categories c- categories_id and its other fields and parent_id field
categories_description cd- categories_id and categories_name fields.
products_to_categories p2c- products_id linked to categories_id fields
products p- products_id field and other details
specials s- specials_status and products_id
我有这个MySQL查询：
SELECT c.categories_id, cd.categories_name, c.parent_id
FROM categories_description cd, categories c
LEFT JOIN products_to_categories p2c on p2c.categories_id = c.categories_id
LEFT JOIN products p ON p.products_id = p2c.products_id
LEFT JOIN specials s ON p.products_id = s.products_id
and s.specials_status = '1'
WHERE c.categories_id = cd.categories_id and cd.language_id= 4
and (c.parent_id = 0 OR c.parent_id = 1059 )
GROUP BY c.categories_id
ORDER by sort_order, cd.categories_name
获取数组之后，这将给出结果：
[1059] => Array
(
[1109] => Name of 1109
[1323] => Name of 1323
[1324] => Name of 1324
[1322] => Name of 1322
[1142] => Name of 1142
)
[0] => Array
(
[1725] => Name of 1725
[1077] => Name of 1077
[95] => Name of 95
[46] => Name of 46
[96] => Name of 96
[1059] => Name of 1059
[1084] => Name of 1084
[1386] => Name of 1386
[1000] => Name of 1000
)
我无法弄清楚如何排除没有活动特价的类别（在本例中为1322）。将LEFT JOIN替换为JOIN：
SELECT c.categories_id, cd.categories_name, c.parent_id
FROM categories_description cd, categories c
JOIN products_to_categories p2c on p2c.categories_id = c.categories_id
JOIN products p ON p.products_id = p2c.products_id
JOIN specials s ON p.products_id = s.products_id
and s.specials_status = '1'
WHERE c.categories_id = cd.categories_id and cd.language_id= 4
and (c.parent_id = 0 OR c.parent_id = 1059 )
GROUP BY c.categories_id
ORDER by sort_order, cd.categories_name
将为子类别提供正确的结果，但会删除我的主要类别：
[1059] => Array
(
[1109] => Name of 1109
[1323] => Name of 1323
[1324] => Name of 1324
[1142] => Name of 1142
)
尝试子查询：
SELECT c.categories_id, cd.categories_name, c.parent_id
FROM categories_description cd, categories c
JOIN ( select c.categories_id, cd.categories_name, c.parent_id FROM categories_description cd, categories c
JOIN products_to_categories p2c on p2c.categories_id = c.categories_id
JOIN products p ON p.products_id = p2c.products_id
JOIN specials s ON p.products_id = s.products_id
and s.specials_status = '1'
WHERE c.categories_id = cd.categories_id and cd.language_id= 4 and c.parent_id = 1059
) derived
WHERE c.categories_id = cd.categories_id and cd.language_id= 4
and (c.parent_id = 0 OR c.parent_id = 1059 )
GROUP BY c.categories_id
ORDER by sort_order, cd.categories_name
仅提供主要类别：
[0] => Array
(
[1725] => Name of 1725
[1077] => Name of 1077
[95] => Name of 95
[46] => Name of 46
[96] => Name of 96
[1059] => Name of 1059
[1084] => Name of 1084
[1386] => Name of 1386
[1000] => Name of 1000
)