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Table of contents
MySQL
MySQL is a relational database management system, developed by the Swedish company MySQL AB, which is a product of Oracle. MySQL is one of the most popular relational database management systems. In terms of WEB applications, MySQL is one of the best RDBMS (Relational Database Management System, relational database management system) application software. MySQL is a relational database management system. Relational databases store data in different tables instead of putting all the data in one big warehouse, which increases speed and improves flexibility. The SQL language used by MySQL is the most commonly used standardized language for accessing databases. MySQL software adopts a dual authorization policy, which is divided into community edition and commercial edition. Due to its small size, fast speed, low overall cost of ownership, especially the open source feature, MySQL is generally chosen as the website for the development of small, medium and large websites. database.
SQL
Structured Query Language (Structured Query Language), referred to as SQL, is a special-purpose programming language. It is a database query and programming language for accessing data and querying, updating and managing relational database systems. Structured Query Language is a high-level non-procedural programming language that allows users to work on high-level data structures. It does not require the user to specify the data storage method, nor does it require the user to understand the specific data storage method, so different database systems with completely different underlying structures can use the same structured query language as the interface for data input and management. Structured query language statements can be nested, which makes it extremely flexible and powerful.
stored function
1). Introduction
CREATE FUNCTION 存储函数名称 ([ 参数列表 ])
RETURNS type [characteristic ...]
BEGIN
-- SQL语句
RETURN ...;
END ; 2). Case
create function fun1(n int)
returns int deterministic
begin
declare total int default 0;
while n>0 do
set total := total + n;
set n := n - 1;
end while;
return total;
end;
select fun1(50);
trigger
introduce
grammar
1). Create
CREATE TRIGGER trigger_name
BEFORE/AFTER INSERT/UPDATE/DELETE
ON tbl_name FOR EACH ROW -- 行级触发器
BEGIN
trigger_stmt ;
END; 2) .View
SHOW TRIGGERS ;3). Delete
DROP TRIGGER [schema_name.]trigger_name ; -- 如果没有指定 schema_name，默认为当前数
据库 。the case
-- 准备工作 : 日志表 user_logs
create table user_logs(
id int(11) not null auto_increment,
operation varchar(20) not null comment '操作类型, insert/update/delete',
operate_time datetime not null comment '操作时间',
operate_id int(11) not null comment '操作的ID',
operate_params varchar(500) comment '操作参数',
primary key(`id`)
)engine=innodb default charset=utf8;A. Insert data trigger
create trigger tb_user_insert_trigger
after insert on tb_user for each row
begin
insert into user_logs(id, operation, operate_time, operate_id, operate_params)
VALUES
(null, 'insert', now(), new.id, concat('插入的数据内容为:
id=',new.id,',name=',new.name, ', phone=', NEW.phone, ', email=', NEW.email, ',
profession=', NEW.profession));
end;test :
-- 查看
show triggers ;
-- 插入数据到tb_user
insert into tb_user(id, name, phone, email, profession, age, gender, status,
createtime) VALUES (26,'三皇子','18809091212','[email protected]','软件工
程',23,'1','1',now());B. Modify data trigger
create trigger tb_user_update_trigger
after update on tb_user for each row
begin
insert into user_logs(id, operation, operate_time, operate_id, operate_params)
VALUES
(null, 'update', now(), new.id,
concat('更新之前的数据: id=',old.id,',name=',old.name, ', phone=',
old.phone, ', email=', old.email, ', profession=', old.profession,
' | 更新之后的数据: id=',new.id,',name=',new.name, ', phone=',
NEW.phone, ', email=', NEW.email, ', profession=', NEW.profession));
end;test :
-- 查看
show triggers ;
-- 更新
update tb_user set profession = '会计' where id = 23;
update tb_user set profession = '会计' where id <= 5;C. Delete data trigger
create trigger tb_user_delete_trigger
after delete on tb_user for each row
begin
insert into user_logs(id, operation, operate_time, operate_id, operate_params)
VALUES
(null, 'delete', now(), old.id,
concat('删除之前的数据: id=',old.id,',name=',old.name, ', phone=',
old.phone, ', email=', old.email, ', profession=', old.profession));
end;test :
-- 查看
show triggers ;
-- 删除数据
delete from tb_user where id = 26; ♥️Following is the driving force for my creation
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