高级资深攻城狮
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题解 | #获取有奖金的员工相关信息。#
总结了两种写法:一种用case when then end,另一种用if(condition,true,false)方法一:select e.emp_no,first_name,last_name,btype,salary,(0.1salary(if(btype>2,3,btype)))fro...
Mysql
2021-09-28
0
255
题解 | #平均工资#
select * from employeeswhere not exists ( select emp_no from dept_emp where emp_no = employees.emp_no);需要将所查询的表和子表关联,不然查不出数据。
Mysql
2021-09-28
0
196
题解 | #平均工资#
select (sum(salary)-max_min.max_s-max_min.min_s)/(count()-2)from salaries,( select max(salary) as max_s,min(salary)as min_s from salaries where...
Mysql
2021-09-28
0
207
题解 | #在last_update后面新增加一列名字为create_date#
delete from titles_test where not id in(select id from titles_test group by emp_no order by id asc)不知道为什么这样就通过了,先以emp_no 分组,按id升序排序,然后删除掉其中id不等于这些最小值...
Mysql
2021-09-27
0
163
题解 | #在last_update后面新增加一列名字为create_date#
create trigger audit_log before insert on employees_testfor each rowbegin insert into audit (emp_no,name) values(new.id,new.name);end;创建触发器语法:creat...
Mysql
2021-09-27
0
280
题解 | #在last_update后面新增加一列名字为create_date#
alter table actor add column create_date datetime not null default"2020-10-01 00:00:00" after last_update在‘last_update’后追加一列,用‘after’指明所要追加的...
Mysql
2021-09-27
0
251
题解 | #针对上面的salaries表emp_no字段创建索引idx_emp_no#
select * from salaries force index (idx_emp_no) where emp_no = 10005强制使用索引 forceindex(“index_name”)select * from table_name force index(“index_name”)w...
Mysql
2021-09-26
0
197
题解 | #针对actor表创建视图actor_name_view#
create view actor_name_view as select first_name as first_name_v,last_name as last_name_v from actor创建视图语法:create view 'view_name' as select 'column1'...
Mysql
2021-09-26
0
228
题解 | #对first_name创建唯一索引uniq_idx_firstname#
Mysql 创建索引的方法:alter table actor add unique uniq_idx_firstname(first_name);alter table actor add index idx_lastname(last_name); sqllite创建索引方法:create u...
Mysql
2021-09-26
0
247
题解 | #创建一个actor_name表#
drop table if exists actor_name;create table actor_name ( first_name varchar(45) not null comment'名字', last_name varchar(45) not null comment'姓氏...
Mysql
2021-09-26
0
204
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