InfoPath Dev

I have 2 dropdown list and get data from shrepoint list. I want once user select data from list A then List B populate. Once user  select data from list B rest of the field from that sharepoint list will populate. I know how to do one dropdown list populate all fields from the list. But how to inbetween another one.

 I my form I have multiplle contracting company and each company has multiple account No. But other field is related account number. I mean account number is primary key. All data stored in sharepoint list and recieve data from there. Customer will Select from dropdown  Contracting company  and that will populate all account number related to that Company in another drop down list. Then customer will Select from 2nd drop down  which will populate rest of teh field.

Please help.

You'll just need multiple filters on your data source when you populate your fields.

When you create your rule, you set a field's value and select your target field. Then, in the formula editor, you select Insert Field or Group and select your source field (that has the data you want in your main data source). When you select that field, you can choose to filter the data.

You'll need two conditions in your filter, with an "and" -- basically saying FieldA in the main data source is equal to the field in the secondary data source that its value is from and FieldB in the main data source is equal to the field in the secondary data source that its value is from.... While this article is about filtering in the drop down data source itself, it does describe using multiple filters, and may be helpful.