MYSQL中動態行數據轉列數據

最近用到城市矩陣相關 須要將城市與城市距離轉化爲二維表 經過動態SQL直接實現 貼出來一塊兒學習：

表就三個字段，包含在sql內。

 
SET @sql:='';

SELECT @sql:=GROUP_CONCAT(item) FROM(
SELECT CONCAT(@sql,'SUM(IF(to_city=\'',to_city,'\'',',distance,0)) AS \'',to_city,'\'') item
FROM (SELECT cm.to_city 
FROM `cities_matrix`  cm  GROUP BY cm.to_city ORDER BY cm.to_city)a
)a
;

SET @sql:=CONCAT('SELECT cm.from_city,',@sql,' FROM cities_matrix cm GROUP BY cm.from_city');
 
PREPARE stmt FROM @sql;  
EXECUTE stmt;