Book table (related table) is related to Category table (primary table). Primary key: CatID. Foreign key: CatID.
ISBN column is the Primary Key for table "Book", so, I've replaced Count(BookID) with Count(ISBN), but all the same:

A fatal error has occured:

GT::SQL::Relation (24951): Bad columns / column clash: columns named 'CatID' have been found in current relation, please qualify your expression. at (eval 30) line 4.

Please enable debugging in setup for more details.

Stack Trace
======================================
Dbsql (24951): GT::Base::error called at GT::SQL::Relation::_complete_name line 1044 with arguments
(GT::SQL::Relation=HASH(0x856a674), BADCOLS, FATAL, CatID).
Dbsql (24951): GT::SQL::Relation::_complete_name called at /home/d/dlovaya/public_html/cgi-bin/admin/GT/SQL/Relation.pm line 242 with arguments
(GT::SQL::Relation=HASH(0x856a674), CatID).
Dbsql (24951): GT::SQL::Relation::select called at (eval 30) line 4 with arguments
(GT::SQL::Relation=HASH(0x856a674), ARRAY(0x856a77c)).
Dbsql (24951): Dbsql::__ANON__ called at /home/d/dlovaya/public_html/cgi-bin/admin/Dbsql/Home.pm line 1506 with arguments
(HASH(0x850f1e0)).
Dbsql (24951): Dbsql::Home::__ANON__ called at /home/d/dlovaya/public_html/cgi-bin/admin/GT/Template.pm line 841 with arguments
(HASH(0x850f1e0)).
Dbsql (24951): GT::Template::_get_var called at /home/d/dlovaya/public_html/cgi-bin/admin/templates/bookstore/compiled/home.html.compiled line 371 with arguments
(GT::Template=HASH(0x8461ac8), countbook, 0, 1).
Dbsql (24951): GT::Template::parsed_template called at /home/d/dlovaya/public_html/cgi-bin/admin/GT/Template.pm line 600 with arguments
(GT::Template=HASH(0x8461ac8)).
Dbsql (24951): GT::Template::_parse called at /home/d/dlovaya/public_html/cgi-bin/admin/GT/Template.pm line 97 with arguments
(GT::Template=HASH(0x8461ac8), home.html, HASH(0x8461a38)).
Dbsql (24951): GT::Template::parse called at /home/d/dlovaya/public_html/cgi-bin/admin/Dbsql/Home.pm line 123 with arguments
(GT::Template, home.html, HASH(0x8461a2c), HASH(0x8461a38)).
Dbsql (24951): Dbsql::Home::print called at /home/d/dlovaya/public_html/cgi-bin/admin/Dbsql/Home.pm line 83 with arguments
(Dbsql::Home=HASH(0x804c14c), home.html, HASH(0x8461a2c)).
Dbsql (24951): Dbsql::Home::process called at /home/d/dlovaya/public_html/cgi-bin/db.cgi line 29 with arguments
(Dbsql::Home=HASH(0x804c14c), in, GT::CGI=HASH(0x8460660), sql, GT::SQL=HASH(0x8526978), cfg, Dbsql::Config=HASH(0x80652ec)).
Dbsql (24951): main::main called at /home/d/dlovaya/public_html/cgi-bin/db.cgi line 22 with no arguments.

Paul