MySQL entry 2 (advanced operation)

  The previous blog mainly introduced the introductory operation of MySQL (adding, deleting, modifying and querying data tables). This blog is to introduce the advanced operations of MySQL, including foreign keys, cascading operations, stored procedures, triggers, etc.

data constraints

 1 What data constraints

   Constrain the data of the user operation table

  1 default

   Function: When the user does not insert a value for the field that uses the default value, the default value is used.

Note:
  1) It is OK to insert null for default value fields.
  2) Non-null can be inserted into the default value field

-- 1.1 默认值
CREATE TABLE student(
    id INT,
    NAME VARCHAR(20),
    address VARCHAR(20) DEFAULT '广州天河'  -- 默认值
)

DROP TABLE student;
-- 当字段没有插入值的时候，mysql自动给该字段分配默认值
INSERT INTO student(id,NAME) VALUES(1,'张三');

-- 注意：默认值的字段允许为null
INSERT INTO student(id,NAME,address) VALUE(2,'李四',NULL);
INSERT INTO student(id,NAME,address) VALUE(3,'王五','广州番禺');

  2 is not empty

Function: Restriction fields must be assigned
Note :
  1) Non-null characters must be assigned
  2) Non-null characters cannot be assigned null

-- 1.2 非空
-- 需求： gender字段必须有值（不为null）
CREATE TABLE student(
    id INT,
    NAME VARCHAR(20),
    gender VARCHAR(2) NOT NULL -- 非空
)

-- 非空字段必须赋值
INSERT INTO student(id,NAME) VALUES(1,'李四');
-- 非空字符不能插入null
INSERT INTO student(id,NAME,gender) VALUES(1,'李四',NULL);

  3 unique

Function: The value of the field cannot be repeated
Note :
  1) The unique field can insert null
  2) The unique field can insert multiple nulls

-- 1.3 唯一
CREATE TABLE student(
    id INT UNIQUE, -- 唯一
    NAME VARCHAR(20)
)

INSERT INTO student(id,NAME) VALUES(1,'zs');
INSERT INTO student(id,NAME) VALUES(1,'lisi'); -- ERROR 1062 (23000): Duplicate entry '1' for key 'id'

INSERT INTO student(id,NAME) VALUES(2,'lisi');

  4 Primary key

Function: non-null + unique
Note :
  1) Normally, each table will set a primary key field. Used to mark the uniqueness of each record in the table.
  2) It is recommended not to select the field containing business meaning of the table as the primary key. It is recommended to design an id field with non-business meaning independently for each table.

-- 1.4 主键（非空+唯一）
DROP TABLE student;

CREATE TABLE student(
    id INT PRIMARY KEY, -- 主键
    NAME VARCHAR(20)
)

INSERT INTO student(id,NAME) VALUES(1,'张三');
INSERT INTO student(id,NAME) VALUES(2,'张三');
-- INSERT INTO student(id,NAME) VALUES(1,'李四'); -- 违反唯一约束： Duplicate entry '1' for key 'PRIMARY'

-- insert into student(name) value('李四'); -- 违反非空约束： ERROR 1048 (23000): Column 'id' cannot be null

  5 Self-growth

Function: auto increment

-- 1.5 自增长
CREATE TABLE student(
    id INT(4) ZEROFILL PRIMARY KEY AUTO_INCREMENT, -- 自增长，从0开始  ZEROFILL 零填充
    NAME VARCHAR(20)
)

-- 自增长字段可以不赋值，自动递增
INSERT INTO student(NAME) VALUES('张三');
INSERT INTO student(NAME) VALUES('李四');
INSERT INTO student(NAME) VALUES('王五');

SELECT * FROM student;
-- 不能影响自增长约束
DELETE FROM student;
-- 可以影响自增长约束
TRUNCATE TABLE student;

  6 foreign keys

Role: Constrain the data of two tables

There are two kinds of tables:
  Solve the problem of high data redundancy: Separate a table
    such as employee table and department table
  Problem: When inserting employee table data, the department ID field of employee table can be inserted at will! ! ! ! !

Using a foreign key constraint: Constraint inserting the department ID field value of the employee table

Solution: Add a foreign key constraint to the department ID field of the employee table

-- 部门表（主表）
CREATE TABLE dept(
    id INT PRIMARY KEY,
    deptName VARCHAR(20)
)

-- 修改员工表（副表/从表）
CREATE TABLE employee(
    id INT PRIMARY KEY,
    empName VARCHAR(20),
    deptId INT,-- 把部门名称改为部门ID
    -- 声明一个外键约束
    CONSTRAINT emlyee_dept_fk FOREIGN KEY(deptId) REFERENCES dept(id)
    --           外键名称                  外键               参考表(参考字段)
)

Note:
1) The constrained table is called the secondary table, the table that constrains others is called the primary table, and the foreign key is set on the secondary table! ! !
2) The reference field of the main table is generally the primary key!
3) Add data: Add the main table first, then add the sub table
4) Modify data: Modify the sub table first, then modify the main table
5) Delete data: Delete the sub table first, then delete the main table

-- 1.6 外键约束
-- 员工表
CREATE TABLE employee(
    id INT PRIMARY KEY,
    empName VARCHAR(20),
    deptName VARCHAR(20) -- 部门名称
)

INSERT INTO employee VALUES(1,'张三','软件开发部');
INSERT INTO employee VALUES(2,'李四','软件开发部');
INSERT INTO employee VALUES(3,'王五','应用维护部');

SELECT * FROM employee;

-- 添加员工，部门名称的数据冗余高
INSERT INTO employee VALUES(4,'陈六','软件开发部');

-- 解决数据冗余高的问题：给冗余的字段放到一张独立表中
-- 独立设计一张部门表
CREATE TABLE dept(
    id INT PRIMARY KEY,
    deptName VARCHAR(20)
)

DROP TABLE employee;

-- 修改员工表
CREATE TABLE employee(
    id INT PRIMARY KEY,
    empName VARCHAR(20),
    deptId INT,-- 把部门名称改为部门ID
    -- 声明一个外键约束
    CONSTRAINT emlyee_dept_fk FOREIGN KEY(deptId) REFERENCES dept(id) ON UPDATE CASCADE ON DELETE CASCADE  -- ON CASCADE UPDATE ：级联修改
    --           外键名称                  外键               参考表(参考字段)
)

INSERT INTO dept(id,deptName) VALUES(1,'软件开发部');
INSERT INTO dept(id,deptName) VALUES(2,'应用维护部');
INSERT INTO dept(id,deptName) VALUES(3,'秘书部');

INSERT INTO employee VALUES(1,'张三',1);
INSERT INTO employee VALUES(2,'李四',1);
INSERT INTO employee VALUES(3,'王五',2);
INSERT INTO employee VALUES(4,'陈六',3);

-- 问题: 该记录业务上不合法，员工插入了一个不存在的部门数据
INSERT INTO employee VALUES(5,'陈六',4); -- 违反外键约束： Cannot add or update a child row: a foreign key constraint fails (`day16`.`employee`, CONSTRAINT `emlyee_dept_fk` FOREIGN KEY (`deptId`) REFERENCES `dept` (`id`))

-- 1）当有了外键约束，添加数据的顺序： 先添加主表，再添加副表数据
-- 2）当有了外键约束，修改数据的顺序： 先修改副表，再修改主表数据
-- 3）当有了外键约束，删除数据的顺序： 先删除副表，再删除主表数据
-- 修改部门(不能直接修改主表)
UPDATE dept SET id=4 WHERE id=3;
-- 先修改员工表
UPDATE employee SET deptId=2 WHERE id=4;

-- 删除部门
DELETE FROM dept WHERE id=2;

-- 先删除员工表
DELETE FROM employee WHERE deptId=2;

SELECT * FROM dept;
SELECT * FROM employee;

  7 Cascade operation

Question: When there is a foreign key constraint, all the associated data in the secondary table must be modified or deleted before the main table can be modified or deleted! However, we want to directly modify or delete the primary table data, thus affecting the secondary table data. This can be achieved using cascading operations! ! !

-- 级联修改： ON UPDATE CASCADE
-- 级联删除： ON DELETE CASCADE

CREATE TABLE employee(
    id INT PRIMARY KEY,
    empName VARCHAR(20),
    deptId INT,-- 把部门名称改为部门ID
    -- 声明一个外键约束
    CONSTRAINT emlyee_dept_fk FOREIGN KEY(deptId) REFERENCES dept(id) ON UPDATE CASCADE ON DELETE CASCADE  -- ON CASCADE UPDATE ：级联修改
    --           外键名称                  外键               参考表(参考字段)
)

Note: Cascading operations must be used on a foreign key basis

-- 级联修改（修改）
-- 直接修改部门
UPDATE dept SET id=5 WHERE id=4;

-- 级联删除
-- 直接删除部门 
DELETE FROM dept WHERE id=1;

Database Design

 1 Introduce

Demand Analysis - Demand Analyst - "Original Demand - > Extract Business Model
     Book Model: Book Name, Version Number, Author
     Student Model: Student ID, Student Name and Mobile Number
     ...
     Role: Student Teacher, Librarian
     "Requirement Specification
" Design-
  Summary Design:
     Extract Entity: Business Model -> Entity Model (java class C++ class) Memory
     class Book{ name, bookNo, author }
     Database Design:
      Business Model/Entity Model -> Data Model (hard disk)

Database table design
     questions: How to design?
  Detailed design
    class details, properties and methods

 2 Three Paradigms

Design principles: It is recommended to design tables that adhere to the three paradigms as much as possible.

First Normal Form: Requires that each field of the table must be an indivisible independent unit

student : name – violates the first normal form
Zhang Xiaoming|Gouwa
sutdent : name old_name – conforms to the first normal form
Zhang

Second Normal Form: On the basis of the first normal form, each table is required to express only one meaning. Each field of the table has a dependency on the primary key of the table.

employee (employee): employee number employee name department name order name - violation of second normal form

Employee table: employee number employee name department name

Order Form: Order Number Order Name – 2nd Normal Form

Third normal form: On the basis of the second normal form, other fields other than the primary key of each table are required to have a direct dependent relationship with the primary key.

Employee table: employee number (primary key) employee name department number department name – conforms to the second normal form, violates the third normal form (high data redundancy)

Employee table: employee number (primary key) employee name department number – conforming to the third normal form (reduce data redundancy)
department table: department number department name

   3Associative query (multi-table query)

--  **************二、关联查询（多表查询）****************----
-- 需求：查询员工及其所在部门(显示员工姓名，部门名称)
-- 2.1 交叉连接查询（不推荐。产生笛卡尔乘积现象：4 * 4=16，有些是重复记录）
SELECT empName,deptName FROM employee,dept;

-- 需求：查询员工及其所在部门(显示员工姓名，部门名称)
-- 多表查询规则：1）确定查询哪些表   2）确定哪些哪些字段   3）表与表之间连接条件 (规律：连接条件数量是表数量-1)
-- 2.2 内连接查询：只有满足条件的结果才会显示(使用最频繁)
SELECT empName,deptName       -- 2）确定哪些哪些字段
    FROM employee,dept    -- 1）确定查询哪些表
    WHERE employee.deptId=dept.id  -- 3）表与表之间连接条件

-- 内连接的另一种语法
SELECT empName,deptName
    FROM employee
    INNER JOIN dept
    ON employee.deptId=dept.id;

-- 使用别名
SELECT e.empName,d.deptName
    FROM employee e
    INNER JOIN dept d
    ON e.deptId=d.id;

-- 需求： 查询每个部门的员工
-- 预期结果：
 --  软件开发部  张三
 --  软件开发部  李四
 --  应用维护部  王五
 --  秘书部      陈六
 --  总经办      null 
-- 2.2 左[外]连接查询： 使用左边表的数据去匹配右边表的数据，如果符合连接条件的结果则显示，如果不符合连接条件则显示null
 -- （注意： 左外连接：左表的数据一定会完成显示！）
SELECT d.deptName,e.empName
    FROM dept d
    LEFT OUTER JOIN employee e
    ON d.id=e.deptId;

-- 2.3 右[外]连接查询: 使用右边表的数据去匹配左边表的数据，如果符合连接条件的结果则显示，如果不符合连接条件则显示null
 -- （注意： 右外连接：右表的数据一定会完成显示！）
SELECT d.deptName,e.empName
    FROM employee e
    RIGHT OUTER JOIN dept d
    ON d.id=e.deptId;

-- 2.4 自连接查询
-- 需求：查询员工及其上司
-- 预期结果：       
    -- 张三    null
    -- 李四    张三
    -- 王五    李四
    -- 陈六    王五
SELECT e.empName,b.empName
    FROM employee e 
    LEFT OUTER JOIN employee b
    ON e.bossId=b.id;

   4 Stored procedures

1 What is a stored procedure
    stored procedure, the sql before the logical sql statement
   has no conditional judgment, and there is no looping
   stored procedure with a flow control statement (if while)
2 Stored procedure features
   1) The execution efficiency is very fast! Stored procedures are executed on the server side of the database! ! !
   2) The portability is very poor! Stored procedures in different databases are not portable.

3 Stored procedure syntax

-- 创建存储过程
DELIMITER $       -- 声明存储过程的结束符
CREATE PROCEDURE pro_test()           --存储过程名称(参数列表)
BEGIN             -- 开始
    -- 可以写多个sql语句;          -- sql语句+流程控制
    SELECT * FROM employee;
END $            -- 结束 结束符

-- 执行存储过程
CALL pro_test();          -- CALL 存储过程名称(参数);

参数：
IN：   表示输入参数，可以携带数据带存储过程中
OUT： 表示输出参数，可以从存储过程中返回结果
INOUT： 表示输入输出参数，既可以输入功能，也可以输出功能


-- **************三、存储过程*******************-
-- 声明结束符
-- 创建存储过程
DELIMITER $
CREATE PROCEDURE pro_test()
BEGIN
    -- 可以写多个sql语句;
    SELECT * FROM employee;
END $

-- 执行存储过程
CALL pro_test();

-- 3.1 带有输入参数的存储过程
-- 需求：传入一个员工的id，查询员工信息
DELIMITER $
CREATE PROCEDURE pro_findById(IN eid INT)  -- IN: 输入参数
BEGIN
    SELECT * FROM employee WHERE id=eid;
END $ 

-- 调用
CALL pro_findById(4);

-- 3.2 带有输出参数的存储过程
DELIMITER $
CREATE PROCEDURE pro_testOut(OUT str VARCHAR(20))  -- OUT：输出参数
BEGIN
        -- 给参数赋值
    SET str='helljava';
END $

-- 删除存储过程
DROP PROCEDURE pro_testOut;
-- 调用
-- 如何接受返回参数的值？？
-- ***mysql的变量******
--  全局变量（内置变量）：mysql数据库内置的变量 （所有连接都起作用）
        -- 查看所有全局变量： show variables
        -- 查看某个全局变量： select @@变量名
        -- 修改全局变量： set 变量名=新值
        -- character_set_client: mysql服务器的接收数据的编码
        -- character_set_results：mysql服务器输出数据的编码

--  会话变量： 只存在于当前客户端与数据库服务器端的一次连接当中。如果连接断开，那么会话变量全部丢失！
        -- 定义会话变量: set @变量=值
        -- 查看会话变量： select @变量

-- 局部变量： 在存储过程中使用的变量就叫局部变量。只要存储过程执行完毕，局部变量就丢失！！

-- 1)定义一个会话变量name, 2)使用name会话变量接收存储过程的返回值
CALL pro_testOut(@NAME);
-- 查看变量值
SELECT @NAME;

-- 3.3 带有输入输出参数的存储过程
DELIMITER $
CREATE PROCEDURE pro_testInOut(INOUT n INT)  -- INOUT： 输入输出参数
BEGIN
   -- 查看变量
   SELECT n;
   SET n =500;
END $

-- 调用
SET @n=10;

CALL pro_testInOut(@n);

SELECT @n;

-- 3.4 带有条件判断的存储过程
-- 需求：输入一个整数，如果1，则返回“星期一”,如果2，返回“星期二”,如果3，返回“星期三”。其他数字，返回“错误输入”;
DELIMITER $
CREATE PROCEDURE pro_testIf(IN num INT,OUT str VARCHAR(20))
BEGIN
    IF num=1 THEN
        SET str='星期一';
    ELSEIF num=2 THEN
        SET str='星期二';
    ELSEIF num=3 THEN
        SET str='星期三';
    ELSE
        SET str='输入错误';
    END IF;
END $

CALL pro_testIf(4,@str);

SELECT @str;

-- 3.5 带有循环功能的存储过程
-- 需求： 输入一个整数，求和。例如，输入100，统计1-100的和
DELIMITER $
CREATE PROCEDURE pro_testWhile(IN num INT,OUT result INT)
BEGIN
    -- 定义一个局部变量
    DECLARE i INT DEFAULT 1;
    DECLARE vsum INT DEFAULT 0;
    WHILE i<=num DO
          SET vsum = vsum+i;
          SET i=i+1;
    END WHILE;
    SET result=vsum;
END $

DROP PROCEDURE pro_testWhile;


CALL pro_testWhile(100,@result);

SELECT @result;

USE day16;

-- 3.6 使用查询的结果赋值给变量（INTO）
DELIMITER $
CREATE PROCEDURE pro_findById2(IN eid INT,OUT vname VARCHAR(20) )
BEGIN
    SELECT empName INTO vname FROM employee WHERE id=eid;
END $

CALL pro_findById2(1,@NAME);

SELECT @NAME;

   5 Triggers

1 Trigger function
When you operate a table, you want to trigger some actions/behaviors at the same time, you can use triggers to complete! !

For example: When inserting a record into the employee table, you want to insert data into the log table at the same time

-- 需求： 当向员工表插入一条记录时，希望mysql自动同时往日志表插入数据
-- 创建触发器(添加)
CREATE TRIGGER tri_empAdd AFTER INSERT ON employee FOR EACH ROW    -- 当往员工表插入一条记录时
     INSERT INTO test_log(content) VALUES('员工表插入了一条记录');

-- 插入数据
INSERT INTO employee(id,empName,deptId) VALUES(7,'扎古斯',1);
INSERT INTO employee(id,empName,deptId) VALUES(8,'扎古斯2',1);

-- 创建触发器(修改)
CREATE TRIGGER tri_empUpd AFTER UPDATE ON employee FOR EACH ROW    -- 当往员工表修改一条记录时
     INSERT INTO test_log(content) VALUES('员工表修改了一条记录');

 -- 修改
 UPDATE employee SET empName='eric' WHERE id=7;

-- 创建触发器(删除)
CREATE TRIGGER tri_empDel AFTER DELETE ON employee FOR EACH ROW    -- 当往员工表删除一条记录时
     INSERT INTO test_log(content) VALUES('员工表删除了一条记录');

 -- 删除
 DELETE FROM employee WHERE id=7;

    6mysql permission problem

-- ***********五、mysql权限问题****************
 -- mysql数据库权限问题：root ：拥有所有权限（可以干任何事情）
 -- 权限账户，只拥有部分权限（CURD）例如，只能操作某个数据库的某张表
 -- 如何修改mysql的用户密码？
 -- password: md5加密函数(单向加密)
 SELECT PASSWORD('root'); -- *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B

--  mysql数据库，用户配置 : user表
USE mysql;

SELECT * FROM USER;

-- 修改密码
UPDATE USER SET PASSWORD=PASSWORD('123456') WHERE USER='root';

-- 分配权限账户
GRANT SELECT ON day16.employee TO 'eric'@'localhost' IDENTIFIED BY '123456';
GRANT DELETE ON day16.employee TO 'eric'@'localhost' IDENTIFIED BY '123456';