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题解 | 触发器的语法及使用

create trigger audit_trigger after insert on employees_test for each row begin insert into audit (EMP_no, NAME) values (NEW.ID, NEW.NAME); #需要...

2024-04-24

0 163

题解 | mysql能用force强索引，不能用use强索引

SELECT * FROM salaries force INDEX (idx_emp_no) WHERE emp_no = '10005';

2024-04-24

0 241

题解 |#创建视图creat view ^ select #

create view actor_name_view as select first_name first_name_v, last_name last_name_v from actor

2024-04-24

0 233

题解 | #对first_name创建唯一索引#

create unique index uniq_idx_firstname on actor (first_name); create index idx_lastname on actor (last_name);

2024-04-24

0 174

题解 | #创建一个actor_name表,复制表数据#

create table actor_name ( first_name varchar(45) not null comment '名字', last_name varchar(45) not null comment '姓氏' ); insert...

2024-04-24

0 184

题解 | INSERT IGNORE INTO

insert ignore into actor (actor_id, first_name, last_name, last_update) values ('3', 'ED', 'CHASE', '2006-02-15 12:34:33')

2024-04-24

0 218

题解 | 给的类型是timestamp，为什么用date才行

CREATE TABLE actor ( actor_id SMALLINT (5) NOT NULL PRIMARY KEY COMMENT '主键id', first_name VARCHAR(45) NOT NULL COMMENT '名字', ...

2024-04-24

0 169

题解 | concat()函数的应用

select concat(last_name, ' ', first_name) as name from employees

2024-04-24

0 234

题解 | left join和is null，只用两张表

SELECT f.film_id, f.title FROM film f LEFT JOIN film_category fc ON f.film_id = fc.film_id WHERE fc.category_id IS NULL;

2024-04-24

0 186

题解 |join+group by+order by解决问题

select d.dept_no, d.dept_name, t.title, count(t.title) count from departments d left join dept_emp e on d.dept_no = e.dept_no ...

2024-04-23

0 231