Order by與group by

• 排序可用 Order by
• select * from main order by name
• select * from main order by sex,name
• DESC 遞減 ASC 遞增
• select * from main order by birthday DESC
• select * from main order by birthday ASC
• DISTINCT 唯一
• select DISTINCT sex FROM main
• GROUP BY 把相同的結果結合在一起
• select cid, sum(num) from sale group by cid