What is the percentage for the Yelp businesses in "Pets" category of all businesses?
businesses in "Pets" category refers to category_name = 'Pets'; percentage refers to DIVIDE(COUNT(category_name = 'Pets'), COUNT(business_id)) * 100%
SELECT CAST(SUM(CASE WHEN T2.category_name = 'Pets' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T2.category_name) FROM Business_Categories AS T1 INNER JOIN Categories AS T2 ON T1.category_id = T2.category_id