[web2py] Why does this not work for mysql?

[simon]

db1 = DAL('sqlite://storage.sqlite', folder='c:/web2py/applications/
crm/databases', auto_import=True)
db2 = DAL('mysql://root@localhost/opencart', auto_import=True)
print(db1.tables)
print(db2.tables)
a=db2.executesql("show tables")
print(a)

This lists the tables for sqlite database; and lists the tables for
mysql with the "show tables" command. However it shows an empty list
for the mysql db.tables.