954
社区成员
发帖
与我相关
我的任务
分享这两种写法有什么不同吗？书上答案推荐第二种
1.
SELECT
COUNT(CASE WHEN hanbai_tanka <= 1000 THEN hanbai_tanka ELSE NULL END) AS low_price,
COUNT(CASE WHEN hanbai_tanka BETWEEN 1001 AND 3000 THEN hanbai_tanka ELSE NULL END) AS mid_price,
COUNT(CASE WHEN hanbai_tanka >= 3001 THEN hanbai_tanka ELSE NULL END) AS high_price
FROM Shohin;
2.
SELECT
SUM(CASE WHEN hanbai_tanka <= 1000 THEN 1 ELSE 0 END) AS low_price,
SUM(CASE WHEN hanbai_tanka BETWEEN 1001 AND 3000 THEN 1 ELSE 0 END) AS mid_price,
SUM(CASE WHEN hanbai_tanka >= 3001 THEN 1 ELSE 0 END) AS high_price
FROM Shohin;
结果都是正确的
SELECT
COUNT(CASE WHEN hanbai_tanka <= 1000 THEN hanbai_tanka ELSE NULL END) AS low_price,
COUNT(CASE WHEN hanbai_tanka BETWEEN 1001 AND 3000 THEN hanbai_tanka ELSE NULL END) AS mid_price,
COUNT(CASE WHEN hanbai_tanka >= 3001 THEN hanbai_tanka ELSE NULL END) AS high_price
FROM Shohin;
2.
SELECT
SUM(CASE WHEN hanbai_tanka <= 1000 THEN 1 ELSE 0 END) AS low_price,
SUM(CASE WHEN hanbai_tanka BETWEEN 1001 AND 3000 THEN 1 ELSE 0 END) AS mid_price,
SUM(CASE WHEN hanbai_tanka >= 3001 THEN 1 ELSE 0 END) AS high_price
FROM Shohin;
结果都是正确的
...全文
请发表友善的回复…
发表回复
洒家洗头用飘柔 2019-01-11
- 打赏
- 举报
楼上说的对。。
siwluxuefeng 2018-11-30
- 打赏
- 举报
1=1当然正确了，不是推荐用哪个，而是应该用哪个
wxf54318 2018-03-28
- 打赏
- 举报
感觉没啥太大区别啊，你可以比较下两种方法的执行效率
