Database: public_review_platform
Question: In businesses with a category of "DJs", how many businesses are rated less than 5?
SQL: SELECT COUNT(T1.business_id) FROM Business AS T1 INNER JOIN Business_Categories AS T2 ON T1.business_id = T2.business_id INNER JOIN Categories AS T3 ON T2.category_id = T3.category_id WHERE T3.category_name = 'DJs' AND T1.stars < 5