选择从其他现有列计算'虚拟'列

Question

是否有可能在sql/sqlite3执行选择的列不存在，但是其他列的计算结果？

例如考虑到与列max和电流的表，我想对之探源进行选择两个，所以如果我有间：

table_data: 
max|current 
10|3 
12|8 

select ???? from table_data order by ????? asc; 

desired result: 
4 
7 

的sqlite3这里语法http://www.sqlite.org/lang_expr.html，但无法理解它

Answer 1

select `max` - `current` as `result` from table_data order by `result` asc 

Answer 2

如果这不仅仅是一次性的，你可能更适合观看。

create view yourtable_diffs as 
select max, current, max - current as diff from yourtable; 

然后，你可以

select diff from yourtable_diffs order by diff; 

你可能需要看看SQL tutorial从FirstSQL J.