; WITH t AS(
SELECT *,row=ROW_NUMBER() OVER(ORDER BY id) FROM Meal
)
UPDATE t SET MealPic= RIGHT(10000+row,3)+'gif'

------解决方案--------------------
SQL code

--猜一个
declare @i int
set @i=1
while @i<100 --假如你要插入100行
begin
    insert into Restaurant.dbo.Meal(MealPic)
    select replicate('0',3-len(cast(@i as varchar(3))))+cast(@i as varchar(3))+'.gif'
    set @i=@i+1
end

------解决方案--------------------
update Meal
set MealPic='00'+convert(varchar(10),id,8)+'.gif'

其中id 为自增列，如果你没有可以加 ROW_NUMBER