SQLite的：......除了... ORDER BY RANDOM（）

Question

這個查詢：

SELECT colour FROM ColourView EXCEPT SELECT colour FROM SkinColourExceptionsView WHERE race = 'Human' ORDER BY RANDOM() LIMIT 1

產生如下異常：1st ORDER BY term does not match any column in the result set

然而，改變ORDER BY RANDOM()到ORDER BY colour能夠產生結果（按顏色按字母順序排序而非隨機排列）。以下暗示ORDER BY RANDOM() LIMIT 1應該工作：Select random row from an sqlite table。有人可以解釋爲什麼我的查詢不起作用嗎？

Answer 1

在compound query中，ORDER BY項（s）必須與結果集中的某個列相匹配。

您可以解決此限制通過移動複合查詢爲子查詢：

SELECT colour 
FROM (SELECT colour FROM ColourView 
     EXCEPT 
     SELECT colour FROM SkinColourExceptionsView WHERE race = 'Human') 
ORDER BY random() 
LIMIT 1; 

或者，重寫查詢，使用不同的過濾機制：

SELECT colour 
FROM ColourView 
WHERE colour NOT IN (SELECT colour 
        FROM SkinColourExceptionsView 
        WHERE race = 'Human') 
ORDER BY random() 
LIMIT 1;