MySQL查詢的表

Question

高值我在results表以下數據：

 
+-----+-----+-----+-----+-----+-----+ 
| A | B | C | D | E | F | 
+-----+-----+-----+-----+-----+-----+ 
| 100 | 140 | 120 | 130 | 160 | 150 | 
| 200 | 243 | 374 | 435 | 674 | 987 | 
| 312 | 324 | 123 | 456 | 378 | 645 | 
+-----+-----+-----+-----+-----+-----+ 

什麼樣SELECT語句可以讓我從結果表中的最高的5個值？

Answer 1

什麼樣的SELECT聲明可以從結果表中得到最高的5個值？

事實上，每一列的處理方式相同表明您的模式是非規範化的。如果數據標準化，這種操作將會大大簡化，從而合併列（但創建一個附加列以指示每個記錄來自哪個列）。

然而，就當前情況來看，你可以使用一個UNION：

(SELECT A col FROM results ORDER BY col DESC LIMIT 5) 
UNION ALL 
    (SELECT B col FROM results ORDER BY col DESC LIMIT 5) 
UNION ALL 
    (SELECT C col FROM results ORDER BY col DESC LIMIT 5) 
UNION ALL 
    (SELECT D col FROM results ORDER BY col DESC LIMIT 5) 
UNION ALL 
    (SELECT E col FROM results ORDER BY col DESC LIMIT 5) 
UNION ALL 
    (SELECT F col FROM results ORDER BY col DESC LIMIT 5) 
ORDER BY col DESC 
LIMIT 5 

看到它的sqlfiddle。