SQL190 某乎问答11月份日人均回答量
题目描述
现有某乎问答创作者回答情况表answer_tb如下(其中answer_date表示回答日期、author_id指创作者编号、issue_id表示问题id、char_len表示回答字数):
answer_date | author_id | issue_id | char_len |
---|---|---|---|
2021-11-01 | 101 | E001 | 150 |
2021-11-01 | 101 | E002 | 200 |
2021-11-01 | 102 | C003 | 50 |
2021-11-01 | 103 | P001 | 35 |
2021-11-01 | 104 | C003 | 120 |
2021-11-01 | 105 | P001 | 125 |
2021-11-01 | 102 | P002 | 105 |
2021-11-02 | 101 | P001 | 201 |
2021-11-02 | 110 | C002 | 200 |
2021-11-02 | 110 | C001 | 225 |
2021-11-02 | 110 | C002 | 220 |
2021-11-03 | 101 | C002 | 180 |
2021-11-04 | 109 | E003 | 130 |
2021-11-04 | 109 | E001 | 123 |
2021-11-05 | 108 | C001 | 160 |
2021-11-05 | 108 | C002 | 120 |
2021-11-05 | 110 | P001 | 180 |
2021-11-05 | 106 | P002 | 45 |
2021-11-05 | 107 | E003 | 56 |
请你统计11月份日人均回答量(回答问题数量/答题人数),按回答日期排序,结果保留两位小数,以上例子的输出结果如下:
answer_date | per_num |
---|---|
2021-11-01 | 1.40 |
2021-11-02 | 2.00 |
2021-11-03 | 1.00 |
2021-11-04 | 2.00 |
2021-11-05 | 1.25 |
SQL Schema
sql
drop table if exists answer_tb;
CREATE TABLE answer_tb(
answer_date date NOT NULL,
author_id int(10) NOT NULL,
issue_id char(10) NOT NULL,
char_len int(10) NOT NULL);
INSERT INTO answer_tb VALUES('2021-11-1', 101, 'E001' ,150);
INSERT INTO answer_tb VALUES('2021-11-1', 101, 'E002', 200);
INSERT INTO answer_tb VALUES('2021-11-1',102, 'C003' ,50);
INSERT INTO answer_tb VALUES('2021-11-1' ,103, 'P001', 35);
INSERT INTO answer_tb VALUES('2021-11-1', 104, 'C003', 120);
INSERT INTO answer_tb VALUES('2021-11-1' ,105, 'P001', 125);
INSERT INTO answer_tb VALUES('2021-11-1' , 102, 'P002', 105);
INSERT INTO answer_tb VALUES('2021-11-2', 101, 'P001' ,201);
INSERT INTO answer_tb VALUES('2021-11-2', 110, 'C002', 200);
INSERT INTO answer_tb VALUES('2021-11-2', 110, 'C001', 225);
INSERT INTO answer_tb VALUES('2021-11-2' , 110, 'C002', 220);
INSERT INTO answer_tb VALUES('2021-11-3', 101, 'C002', 180);
INSERT INTO answer_tb VALUES('2021-11-4' ,109, 'E003', 130);
INSERT INTO answer_tb VALUES('2021-11-4', 109, 'E001',123);
INSERT INTO answer_tb VALUES('2021-11-5', 108, 'C001',160);
INSERT INTO answer_tb VALUES('2021-11-5', 108, 'C002', 120);
INSERT INTO answer_tb VALUES('2021-11-5', 110, 'P001', 180);
INSERT INTO answer_tb VALUES('2021-11-5' , 106, 'P002' , 45);
INSERT INTO answer_tb VALUES('2021-11-5' , 107, 'E003', 56);
答案
sql
SELECT answer_date, ROUND(COUNT(issue_id) / COUNT(DISTINCT author_id), 2) AS `per_num`
FROM answer_tb
WHERE MONTH(answer_date) = 11
GROUP BY answer_date
ORDER BY answer_date;