I don’t know of a way to do it if you are using CF7. This is because you use the CF7 short code to generate the form HTML but we would need to change how the form HTML is generated.
Alternatively, if you were to create your own form by writing your own HTML (not using CF7), then you could do it. In that case you would also have to add a short code for CFDB to capture the data (see https://cfdbplugin.com/?page_id=508).
In such a case, you create the form HTML and use a short code to fill out the choices in part of the form. For example, you have a form like this:
[cfdb-save-form-post]
<form action="" method="post">
<input type="hidden" name="form_title" value="Registration"/>
First Name: <input type="text" name="fname" value=""/><br/>
Last Name: <input type="text" name="lname" value=""/><br/>
<select name="Team">
<option value="Team1">Team1</option>
<option value="Team2">Team2</option>
<option value="Team3">Team3</option>
</select><br/>
<input type="submit" />
</form>
But you want the Team option values to be populated by a short code that pulls team names from CFBD that were submitted previously in a “Teams” form that had “team_name” fields, then you could replace the option tags with a short code like:
[cfdb-save-form-post]
<form action="" method="post">
<input type="hidden" name="form_title" value="Registration"/>
First Name: <input type="text" name="fname" value=""/><br/>
Last Name: <input type="text" name="lname" value=""/><br/>
<select name="Team">
[cfdb-html form="Teams" show="team_name"]
<option value="${team_name}">${team_name}</option>
[/cfdb-html]
</select><br/>
<input type="submit" />
</form>
There is a more complex case involving a “cascading” where you might have a “state” list and based on the user’s selection of that, “city” field choices automatically update to be consistent with the state choice. That case would require writing some Javascript and making AJAX calls that effectively do what the short code does, it just does it on the fly.