基本語法

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE condition
GROUP BY column_name

範例一：遊戲統計資料彙總

原始資料：

gameid	best	top	spam
111	1	1	1
121	1	1	0
123	0	1	1
111	1	0	1

查詢：

SELECT gameid,
       SUM(best) AS bestcnt,
       SUM(top) AS topcnt,
       SUM(spam) AS spamcnt
FROM table
GROUP BY gameid

結果：

gameid	bestcnt	topcnt	spamcnt
111	2	1	2
121	1	1	0
123	0	1	1

PHP 中使用範例

$sql = "SELECT gameid,
               SUM(best) AS best,
               SUM(top) AS top,
               SUM(spam) AS spam
        FROM tablename
        GROUP BY gameid
        ORDER BY gameid ASC";

範例二：勝負統計

使用 DECODE（Oracle）或 CASE WHEN（通用）將勝負轉為數值後加總：

SELECT 日期,
       SUM(CASE WHEN 勝負='勝' THEN 1 ELSE 0 END) AS 勝,
       SUM(CASE WHEN 勝負='負' THEN 1 ELSE 0 END) AS 負
FROM 數據庫表
GROUP BY 日期