阿莉勒丝黛拉

题解

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题解 | #统计作答次数#

SELECT COUNT(exam_id) total_pv, COUNT(submit_time) complete_pv, COUNT(DISTINCT IF(submit_time ...

Mysql

2022-03-11

1 342

题解 | #SQL类别高难度试卷得分的截断平均值#

SELECT ei.tag, ei.difficulty, ROUND( (SUM(er.score) - (MAX(er.score) + ...

Mysql

2022-03-11

1 287

题解 | #删除索引#

ALTER TABLE examination_info DROP INDEX uniq_idx_exam_id; ALTER TABLE examination_info DROP&nbs...

Mysql

2022-03-11

1 300

题解 | #创建索引#

CREATE INDEX idx_duration ON examination_info(duration); CREATE UNIQUE INDEX uniq_idx_exam_id ON examina...

Mysql

2022-03-11

1 286

题解 | #删除表#

DROP TABLE IF EXISTS exam_record_2011; DROP TABLE IF EXISTS exam_record_2012; DROP TABLE IF EXI...

Mysql

2022-03-11

1 330

题解 | #修改表#

这一题是运气题，同样的答案提交多次才通过。 ALTER TABLE user_info ADD school VARCHAR(15) AFTER level; ALTER TABLE user_info&n...

Mysql

2022-03-11

2 960

题解 | #创建一张新表#

CREATE TABLE IF NOT EXISTS user_info_vip ( id INT(11) NOT NULL AUTO_INCREMENT COMME...

Mysql

2022-03-10

1 389

题解 | #删除记录（二）#

DELETE FROM exam_record WHERE submit_time IS NULL &nbs***bsp;TIMESTAMPDIFF(MINUTE, start_time, ...

Mysql

2022-03-10

1 252

题解 | #删除记录（一）#

DELETE FROM exam_record WHERE TIMESTAMPDIFF(MINUTE, start_time, submit_time) < 5 AND&n...

Mysql

2022-03-10

1 341

题解 | #更新记录（二）#

UPDATE exam_record SET submit_time = '2099-01-01 00:00:00', score = 0 WHERE s...

Mysql

2022-03-10

1 342