mysql中如何將2張表聯立排序？

SELECT * FROM (SELECT id,ach,'X' AS counter,'A' AS class,date FROM tablename1 as t1 WHERE 1 UNION SELECT id,ach,counter,'B' AS class,date FROM tablename2 as t2 WHERE 1) AS tall order by date asc

建議增加條件,且為索引字段.其次查的數據量不能太大,不然臨時表會占據較多的內存空間.寧可犧牲硬盤空間,也不要無謂的犧牲內存空間.

從長遠角度來說,建議整合2個表.