MySQL在計算上排序

Question

是否可以對mySQL中的2行進行排序？例如，我有2行，lp和ap我試圖做這樣的事情：

SELECT * from myTbl WHERE 1 ORDER BY (lp/ap) 

哪一個不是拋出一個錯誤，但它也並不是由計算的結果進行排序。有沒有辦法做到這一點，或者我必須將lp/ap存儲在數據庫中？

Answer 1

是的，這是可能的，而且它的工作。看看下面的測試：

CREATE TABLE a(a INT, b INT); 

INSERT INTO a VALUES (1, 1); 
INSERT INTO a VALUES (1, 2); 
INSERT INTO a VALUES (1, 3); 
INSERT INTO a VALUES (1, 4); 
INSERT INTO a VALUES (1, 5); 
INSERT INTO a VALUES (1, 6); 
INSERT INTO a VALUES (2, 1); 
INSERT INTO a VALUES (2, 2); 
INSERT INTO a VALUES (2, 3); 
INSERT INTO a VALUES (2, 4); 
INSERT INTO a VALUES (2, 5); 
INSERT INTO a VALUES (2, 6); 

SELECT a.a, a.b, (a/b) FROM a ORDER BY (a/b); 

+------+------+--------+ 
| a | b | (a/b) | 
+------+------+--------+ 
| 1 | 6 | 0.1667 | 
| 1 | 5 | 0.2000 | 
| 1 | 4 | 0.2500 | 
| 2 | 6 | 0.3333 | 
| 1 | 3 | 0.3333 | 
| 2 | 5 | 0.4000 | 
| 1 | 2 | 0.5000 | 
| 2 | 4 | 0.5000 | 
| 2 | 3 | 0.6667 | 
| 2 | 2 | 1.0000 | 
| 1 | 1 | 1.0000 | 
| 2 | 1 | 2.0000 | 
+------+------+--------+ 

SELECT a.a, a.b FROM a ORDER BY (a/b);會返回相同的結果。

Answer 2

SELECT *, (lp/ap) AS calculation from myTbl ORDER BY calculation 

如果（lp/ap）有效，這應該有效。

Answer 3

你可能有更多的機會做

SELECT *, (lp/ap) as n from myTbl ORDER BY n