求Sql语句

Question

问题1：用Formular Expression新建字段 toText({表名.a}/{表名.b},"###.000")问题2：Select DateDiff(Day,DateAdd(Day,1-DatePart(Day,'2002-10-12'),'2002-10-12'),DateAdd(Day,1-DatePart(Day,DateAdd(Month,1,'2002-10-12')),DateAdd(Month,1,'2002-10-12')))问题3：
Declare @n Numeric(15,3)
Select @n=0.000
Select 日期 , 车间  ,月产量   ,高压蒸汽  ,
       累计高压蒸汽=@n=@n+Round(IsNull((高压蒸汽/月产量),0),3)
From 表
Order By 日期 ASC