条件使用滞后和领先的Sql操作

Question

我有一个如下表（示例数据）

http://sqlfiddle.com/#!18/21e55/1

我要进行超前和滞后运算，

条件1：-当前和以前（名称，月份和年份）相同且

条件2：-

A。如果存在阶段1和2，则计算

Stage number 2 = (Current row target value of stage 2 / previous row target value of stage 1)

B。如果存在阶段编号2，并且存在任何阶段编号（如阶段编号3或4或5），则计算

Stage number 3 = (Current row target value of stage 3 / previous row target value of stage number 2)

Stage number 4 = (Current row target value of stage 4 / previous row target value of stage number 2)

Stage number 5 = (Current row target value of stage 5 / previous row target value of stage number 2)

因此，我的输出应如下所示： http://sqlfiddle.com/#!18/8133c/1