logic

Hi experts

I have orderno itemno and qty in table , I need to find out the

average qty for all itemno for particular orderno.

example

orderno itemno qty avg

001--

---

10

---

5 ----2

001--

---

20

---

5 ----

002--

---

10

---

10 ----7.5

002--

---

20--

---

5

I need to extract data from the table and do the cal

pls give me the logic to do this

karthik