sql-server - 我可以使用 SQL 的 CURSOR 检索前一行的值吗？

Question

我正在开发一个查询，我需要我当前行的某个字段是“我当前行的字段”+“上一行的相同字段”的结果。 (SQL Server 2008)

如何使用游标来完成？

Answer 1

将上一行值赋给一个变量:

declare @previosvalue varchar(100) = null;
declare @currentvalue varchar(100);

declare crs cursor for select value from table;
open crs;

fetch next from crs into @currentvalue;
while @@fetch_status = 0
begin
   -- process here. On first row, @previousvalue is NULL
   -- as it should be, since there is no 'previous' of first

   select ... from sometable
   where somecondition = @currentvalue
   and othercondition = @previousvalue;

   set @previousvalue = @currentvalue;
   fetch next from crs into @currentvalue;
end

close crs;
deallocate crs;