Mysql按照字段值做分組行轉列查詢

今天做個后台服務，有個需求是批量生成一批表的數據，如果用BulkInsert會提升很大一截提交效率，但是如果用循環構造提交的Datable，則算法開銷太高，所以用這種查詢批量查出符合格式的DataTable結果集。

*思想就是將查詢列做CASE判斷值，然后放在 SELECT段中作為別名列顯示字段值，然后再根據ID分組。

下面是內層的原始查詢效果:

下面是行轉列后查詢效果如圖:

 

下面是上面兩張圖的最終查詢語句:

SELECT f_gameID,SUM(score) AS totNum,
    SUM(CASE f_sub WHEN '01' THEN score ELSE 0 END) AS f_subject01,SUM(CASE f_sub WHEN '02' THEN score ELSE 0 END) AS f_subject02,
    SUM(CASE f_sub WHEN '03' THEN score ELSE 0 END) AS f_subject03,SUM(CASE f_sub WHEN '04' THEN score ELSE 0 END) AS f_subject04,
    SUM(CASE f_sub WHEN '05' THEN score ELSE 0 END) AS f_subject05,SUM(CASE f_sub WHEN '06' THEN score ELSE 0 END) AS f_subject06,
    SUM(CASE f_sub WHEN '07' THEN score ELSE 0 END) AS f_subject07,SUM(CASE f_sub WHEN '08' THEN score ELSE 0 END) AS f_subject08,
    SUM(CASE f_sub WHEN '09' THEN score ELSE 0 END) AS f_subject09
FROM 
(
    SELECT u.f_gameID,u.f_sub,COUNT(u.f_sub) AS score
    FROM t_mfg_GameUserAnswers AS u
    LEFT JOIN t_mfg_Class AS c ON u.f_gameId = c.f_gameId
    WHERE u.f_startTime > '2015-07-20' 
    AND u.f_endTime < '2015-07-24'
    -- AND c.f_schoolId = 193034
    GROUP BY u.f_gameID ,u.f_sub
) AS a
GROUP BY f_gameID;