这应该工作

update content,(  select   @row_number:=ifnull(@row_number, 0)+1 as new_position,  ContentID   from content  where CategoryID=1  order by position) as table_positionset position=table_position.new_positionwhere table_position.ContentID=content.ContentID;

但我更喜欢先应用此方法，以取消设置用户定义的变量

set @row_number:=0;

由Mchl添加：

您可以在这样的一条语句中做到这一点

update content,(  select   @row_number:=ifnull(@row_number, 0)+1 as new_position,  ContentID   from content  where CategoryID=1  order by position) as table_position,(  select @row_number:=0) as rowNumberInitset position=table_position.new_positionwhere table_position.ContentID=content.ContentID;