I don't think any of the field types lets you bind to a data source in the
way I think you are looking for.

If you want to fill fields with data directly from SQL Server using built-in
facilities then I think your only options are
a. use old-style DATABASE fields
b. set your document up as a Mail merge main document with a SQL Server
data source and use Mailmerge fields to include the data. however, all the
data at any one time would then have to come from a single record in
whatever view or table you are using as your data source.

(a) used to be feasible, although probably impractical in most cases for
performance reasons, because if you specified a DATABASE field that only
displayed one value (i.e. one column, one row, no header) Word would show
the result as inline text rather than as a single-cell table. Now, however,
you cannot do this because the field result is always followed by a
paragraph mark. There is a workaround for dates and numbers (see e.g.
http://tips.pjmsn.me.uk/t0004.htm)

For something that looks more like "binding", you have to use Word 2007
content controls. But then you can only bind (as far as I know) to the
internal XML data store held as a "part" in the .docx file. In other words,
you have to populate that data store separately using (say) VB.NET, C# or
perhaps VBA code, but when you do, the content of the controls should
reflect the data in the store more or less immediately. But you can put
whatever you wantin the store, and populate it from wherever you want.