条件控制
CASE validity_date WHEN 1 THEN ‘月‘ WHEN 2 THEN ‘年‘ ELSE ‘季‘ END
CASE WHEN validity_date = 1 THEN ‘月‘ WHEN validity_date = 2 THEN ‘年‘ ELSE ‘季‘ END
循环控制
待补充
mysql 逻辑控制
原文：https://www.cnblogs.com/xiaochongc/p/11316348.html
