Recursive query for Product Tree

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I have product tree for a product

product_tree table :
product_code, stock_code, amount_ratio
152.001.001,  151.001.001, 1
152.001.001,  150.001.001, 2
151.001.001   150.003.003, 3
151.001.001   150.009.001, 1


I need to write a query with result:

152.001.001,  150.003.003, 1
152.001.001,  150.009.001, 1
152.001.001,  150.001.001, 2


i.e. for 151 we have another node and i do not wanna see 151 here...but its 
ingredients..

it is kind of recursive query how can i write it ? any help?

Thx in advance

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