WW在搜寻
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题解 | #统计作答次数#
SELECT MIN( er.score ) min_score_over_avg FROM exam_record er JOIN examination_info ei ON er.exam_id = ei.exam_id WHERE ei.tag='SQL' AND er.score>...
Mysql
2022-01-19
0
268
题解 | #统计作答次数#
SELECT DISTINCT ei.tag,ei.difficulty,ROUND((SUM(er.score)-MAX(er.score)-MIN(er.score))/(COUNT(er.score)-2),1) clip_avg_score FROM examination_info ei...
Mysql
2022-01-19
0
209
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
180
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
272
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
322
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
223
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
315
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
278
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