php - SQL ORDER BY AS 变量

Question

我有一个这样的sql查询：

SELECT

.....
price

..... AS distance

ORDER BY case
  ...

我的问题是，如何将计算出的距离用作排序元素？

Answer 1

我不清楚问题查询中的“距离”是什么，以及您为什么将案例放在 oeder by 中。

通常，您可以在 ORDER BY 子句中通过别名或在 select 子句中的编号来提及字段。您也可以将一些逻辑放入 ORDER BY

  select A,
         B as MyB,
         C - Z, -- <- Field #3: (A - #1, B - #2, C - Z - #3, D + F + G - #4 etc)
         D + F + G
    from MyTable
order by MyB asc,       -- <- by alias
         3 desc,        -- <- by field's number
         D + F + G asc, -- <- by some logic, here it's just copy + paste
         case           -- <- by some logic designed for ORDER BY only
           when (A > B + C) then
             1
           when (A > B)  then
             2
           else    
             3
         end desc

Answer 2

distance在order by子句中使用相同的定义：

select 
...
price
<some logic here> as distance
...
order by <same logic here>

或从外部引用派生列select：

select * from
(
select
...
price
... as distance
...
) x
order by x.distance