WW在搜寻
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题解 | #统计作答次数#
SELECT COUNT(start_time) total_pv,COUNT(submit_time) complete_pv,(SELECT COUNT(DISTINCT exam_id) FROM exam_record WHERE submit_time IS NOT NULL) ompl...
Mysql
2022-01-18
0
183
题解 | #创建索引#
#在duration列创建普通索引idx_duration create index idx_duration on examination_info(duration); #在exam_id列创建唯一性索引uniq_idx_exam_id create unique index uniq_idx_...
Mysql
2022-01-18
0
148
题解 | #删除表#
#方式一: /DROP TABLE exam_record_2012; DROP TABLE exam_record_2013; DROP TABLE exam_record_2014;/ #方式二 drop table if exists exam_record_2011,exam_record_...
Mysql
2022-01-17
0
274
题解 | #修改表#
alter table user_info add school varchar(15) after level; alter table user_info change job profession varchar(10); alter table user_info modify achiev...
Mysql
2022-01-17
0
195
题解 | #创建一张新表#
create table if not exists user_info_vip( id int(11) not null primary key auto_increment comment '自增ID', uid int(11) not null unique comment '用户ID', n...
Mysql
2022-01-17
0
323
题解 | #删除记录(一)#
DELETE FROM exam_record WHERE TIMESTAMPDIFF(MINUTE, start_time, submit_time) < 5 AND score<60; 最主要的是 TIMESTAMPDIFF(MINUTE, start_time, submit_ti...
Mysql
2022-01-16
0
224
题解 | #插入记录(二)#
INSERT INTO exam_record_before_2021(uid,exam_id,start_time,submit_time,score) SELECT uid,exam_id,start_time,submit_time,score FROM exam_record WHERE Y...
Mysql
2022-01-15
0
318
题解 | #插入记录(一)#
INSERT INTO exam_record (uid,exam_id,start_time,submit_time,score) VALUES (1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90), (1002,9002,'2021...
Mysql
2022-01-15
0
279
题解 | #浙大不同难度题目的正确率#
SELECT qd.difficult_level,SUM(if(qpd.result='right',1,0))/COUNT(qpd.device_id) AS corrct_rate FROM user_profile up JOIN question_practice_detail qpd O...
Mysql
2022-01-15
0
238
题解 | #统计复旦用户8月练题情况#
SELECT up.device_id,'复旦大学',COUNT(qpd.question_id),SUM(CASE WHEN qpd.result='right' THEN 1 ELSE 0 END) FROM user_profile up LEFT JOIN question_practice...
Mysql
2022-01-15
0
222
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