How many crime cases have been classified as "Weapons Violation" by the FBI?
"Weapons Violation" is the title of crime; crime cases refers to report_no;
SELECT SUM(CASE WHEN T2.title = 'Weapons Violation' THEN 1 ELSE 0 END) FROM Crime AS T1 INNER JOIN FBI_Code AS T2 ON T1.fbi_code_no = T2.fbi_code_no