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作者 vvrr 在 PTT [ Database ] 看板的留言(推文), 共11則

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[SQL ] 有兩個資料表設計的問題

[ Database ]3 留言, 推噓總分: 0

作者: xfighter - 發表於 2013/12/25 16:31(12年前)

1^F→vvrr:case1,我會做成「每個課id只放一門課」，然後A生選多門課就有12/25 17:15

2^F→vvrr:多筆資料。12/25 17:15

3^F→vvrr:case2.我會把lesson_name的日期和課名拆開成兩欄，課名改成id12/25 17:17

Re: [SQL ] 關於再排序與效率的問題

[ Database ]10 留言, 推噓總分: 0

作者: cutekid - 發表於 2013/11/25 09:41(12年前)

1^F→vvrr:這樣是將全部資料先照男女排，再各自按count排序11/25 15:57

2^F→vvrr:取前100名的結果會變成「取到男生(或女生)最多的100名」11/25 15:58

3^F→vvrr:和我希望的「將前100名按男女分開」不一樣......11/25 15:59

5^F→vvrr:假設100男100女，count各自都是從1~10011/25 17:00

6^F→vvrr:我希望拿到的是「男100~男51, 女100~女51」共100名11/25 17:00

7^F→vvrr:你的寫法會找到「男100~男1」或是「女100~女1」(看男女哪個先11/25 17:01

10^F→vvrr:應該會拿到100個男生，也是我想要的答案11/26 11:55

[SQL ] 關於再排序與效率的問題

[ Database ]4 留言, 推噓總分: +1

作者: vvrr - 發表於 2013/11/22 18:21(12年前)

2^F→vvrr:@@"我再檢查看看…因為原本的table比較大，我把無關的拿掉了y11/22 18:49

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