Grouping By SUM from two Table and Subtracting Them Prob

[razin223]

Table  - SELL

------------------------------

|  model  |  quantity |

----------------------------

|  C            |    500    |

|  B          |    500    |

|  C            |  300    |

|  B          |  200    |

-----------------------------

 

 

Table - BUY

 

------------------------------

|  model  | quantity  |

-------------------------------

|  A          |    2000  |

|  B          |    2000  |

|  C          |    2000  |

|  A          |    1000  |

-------------------------------

 

I need to SUM of SELL  and BUY both Group By.

Then I need to subtract them as (BUY - SELL) so I can have the

current status of my stock. Just like this

 

----------------------------

|  model  | quantity  |

-------------------------------

|  A          |    3000    |

|  B          |    1300    |

|  C          |    1200    |

---------------------------------

 

Now how can I do it?My Mysql version is 5.1

[joel24]

something along these lines

SELECT b.model, SUM(b.quantity) - SUM(s.quantity) AS currentQuantity 
FROM sell s 
JOIN buy b ON s.model=b.model
GROUP BY b.model