三级联表查询代码实例

SELECT 
cat1.id id1,
cat1.name name1,

cat2.id id2,
cat2.name name2,

cat3.id id3,
cat3.name name3

FROM mall_goods_cat cat1
         LEFT JOIN mall_goods_cat cat2 on cat1.id = cat2.parent_id
         LEFT JOIN mall_goods_cat cat3 on cat2.id = cat3.parent_id
WHERE cat1.parent_id = 0