有一张stock库存表，里面type字段为1的为采购，2为出库，其余主要字段有stockid，productid和updatetime
另有一张product表，里面有所有的productid，productname
应该如何查询在5月份内未采购或者未出库的product呢？
结果如下图
------解决方案--------------------
- SQL code
SELECT A.productid AS 药品ID,A.productname AS 药品名, CASE WHEN NOT EXISTS(SELECT 1 FROM stock WHERE productid=A.productid AND type='1' AND month(updatetime)=5) THEN '未采购' END AS remark, CASE WHEN NOT EXISTS(SELECT 1 FROM stock WHERE productid=A.productid AND type='2' AND month(updatetime)=5) THEN '未出库' END AS remark2FROM product a