样式一:
SELECT DATE_FORMAT(CURRENT_DATE, 'Y-M') AS `month`,count(class_name) from t3
where DATE_FORMAT(updatetime,'Y-M')=DATE_FORMAT(add_months((CURRENT_DATE),0),'Y-M')
UNION
SELECT DATE_FORMAT(add_months((CURRENT_DATE),-1),'Y-M') AS `month`,count(class_name) from t3
where DATE_FORMAT(updatetime,'Y-M')=DATE_FORMAT(add_months((CURRENT_DATE),-1),'Y-M')
UNION
SELECT DATE_FORMAT(add_months((CURRENT_DATE),-2),'Y-M') AS `month`,count(class_name) from t3
where DATE_FORMAT(updatetime,'Y-M')=DATE_FORMAT(add_months((CURRENT_DATE),-2),'Y-M')
UNION
SELECT DATE_FORMAT(add_months((CURRENT_DATE),-3),'Y-M') AS `month`,count(class_name) from t3
where DATE_FORMAT(updatetime,'Y-M')=DATE_FORMAT(add_months((CU