How to find data in Dynamics GP
Dex SQL Logging
Open the Dex.ini (in the Data folder under Dynamics) and locate these settings, set them to TRUE. These settings will cause Dynamics to generate a DexSQL.log file in the same directory. CAREFUL... if you forget to turn this off, this file will grow until the drive fills up.
DexSQL.log will have all the communications from Dynamics to SQL

DynDeveloper Table reference
Be sure that you're familiar with the table reference on this site. It really is a wonderful resource, it contains a wealth of information.
If you're reading this you have access to this wonderful resource (unashamed plug). We have both descriptions of the tables, and descriptions of the fields in the tables. We begin with the native Dynamics documentation and add contributions by thousands of DynDeveloper users. You are encouraged to help make this resource better by using the Wiki functionality. Notice the 'edit' link next to the field notes in the second screen shot, below.


The 'Table Import' technique
Open the form that you'd like information on and click on Tools > Customize > Table import. The Select A Table dialog that pops up contains all the tables used in this form. Once you get a likely table name, look it up in the DynDeveloper table reference (see above) to get the actual table name.

The Modifier Technique
If you have a license for the customization tools, you'll be able to TOOLS > CUSTOMIZE > MODIFY CURRENT WINDOW. This will open Modifier. In Modifier, you'll find a Form Definition window that is usually hidden behind the form when you open it initially. The Tables tab contains all the tables used in the window. It's... kind of verbose. The screen shot shows the Employee Additional Info form and it lists quite a few tables. But only UPR00100 is really used.


The Table Reference in GP
Clicking on Tools > Resource Descriptions > Tables will give you the native Dynamics table reference functionality. I find it easiest to always sort by Physical Name, personally



The eOne Table Finder
If installed, you'll see the eOne Table Finder under the Tools menu. This is an amazing window that allows you to find a field from a window point of view. Note in the screen shot below I looked up the User Defined fields on the Employee Additional form and Table Finder actually wrote the query to show me where the field was in SQL. Nice.
This functionality requires a license for the eOne product.
http://www.eonesolutions.com/blog-post/smartlist-builder-2013-new-feature-of-the-day-table-finder/

