Planned Orders's order (level) infomations

Hi, all.

I would like to know Planned Orders's order (level) infomations which created by MRP.

for example...

First, 90000101 is released, and goods receipt,

Next (After 90000101), 90000102 is released...

I would like to know which order is first in ABAP.

If you know a table name or function module, let me know please.

thanks.