Alina_0229

题解

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题解 | #获取所有非manager的员工emp_no#

select employees.emp_no from employees left join dept_manager on employees.emp_no = dept_manager.emp_no where dept_manager. dept_no is null 两表进行关联,使用左...

Mysql

2022-03-18

1 298

题解 | #查找薪水记录超过15条的员工号emp_no以及其对应的记录次数t#

根据题意得知，想要查找的是薪水记录超过15条的员工号及对应的次数，所以这里要进行分组，分组的依据是emp_no,同时也要统计相应的次数，分组后的过滤使用的是having select emp_no,count(emp_no) t from salaries group by emp_no havin...

Mysql

2022-03-18

1 249

题解 | #查找当前薪水详情以及部门编号dept_no#

select sr.emp_no, sr.salary , sr.from_date,sr.to_date, dm.dept_no from salaries sr right join dept_manager dm on sr.emp_no=dm.emp_no order by emp_no 看...

Mysql

2022-03-18

1 221

题解 | #查找入职员工时间排名倒数第三的员工所有信息#

select * from employees where hire_date = (select distinct hire_date from employees order by hire_date desc limit 1 offset 2); SELECT * FROM employees...

Mysql

2022-03-18

1 243

题解 | #删除索引#

使用alter 进行删除 alter table 表名 drop index 索引名 ALTER TABLE examination_info DROP INDEX uniq_idx_exam_id; ALTER TABLE examination_info DROP INDEX full_idx_...

Mysql

2022-03-15

0 0

题解 | #创建索引#

以修改表的方式创建索引 alter table examination_info add index idx_duration(duration);#普通索引 alter table examination_info add unique uniq_idx_exam_id(exam_id); #唯一...

Mysql

2022-03-15

0 228

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 CHANGE COLUMN...

Mysql

2022-03-14

0 225

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', nic...

Mysql

2022-03-14

0 236

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

2022-03-14

0 204

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

2022-03-12

0 203