How can I tell if a fieldtype is in use?

Question

I'm trying to clean up my EE install and there are a few third-party fieldtypes that I'm reasonably sure aren't in use. But I'd like to make sure before removing them. Is there any way to tell, other than a manual check of all fields (including all fields in grids)?

Answer 1

This MySQL query should give you a list of fieldtypes which are not currently in use as Channel or Grid fields:

SELECT name FROM exp_fieldtypes WHERE 
    (SELECT COUNT(*) FROM exp_channel_fields WHERE field_type = name) = 0 
AND
    (SELECT COUNT(*) FROM exp_grid_columns WHERE col_type = name) = 0