基於列名的PHP/MySQL匹配單元格

Question

我有一個看起來像這樣的數據庫。

x 2 3 4 5 
4 8 12 16 20 
5 10 15 20 25 
6 12 18 24 30 
7 14 21 28 35 

當一個值的終端用戶插頭欲x變量的值相匹配的x列和其他變量的數值列名。

那麼我該如何去編寫一個SQL查詢來做到這一點？

SELECT * FROM times_tables WHERE x=4 and COLUMN_NAME=4; 

謝謝:)

Answer 1

SELECT 
    `4` 
FROM 
    (SELECT 
     4 as `x`, 8 as `2`, 12 as `3`, 16 as `4`, 20 as `5` 
    UNION ALL 
     SELECT 5, 10, 15, 20, 25 
    UNION ALL 
     SELECT 6, 12, 18, 24, 30 
    UNION ALL 
     SELECT 7, 14, 21, 28, 35) `times_tables` 
WHERE 
    `x` = 4 

輸出：

4 
--- 
16 

所以你的情況的查詢可能是這樣的：

SELECT `{$col}` FROM `times_tables` WHERE `x` = {$row}; 

UPD：

可能與純SQL來完成：

SET @r = 4; -- row 
SET @c = 5; -- col 

SET @qry = CONCAT('SELECT `', @c ,'` FROM `times_tables` WHERE `x` = ', @r); 

PREPARE stmt FROM @qry; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 

P.S：，你可以換到SQL存儲過程中得到更好的保護。