DML、TCL与视图

DML、TCL与视图

  • DML
      • 简介
      • 插入数据
      • 更新数据
      • 删除数据
      • 综合练习
  • TCL(事务控制语言)
      • 事务的隔离级别:
      • 演示事务的使用步骤:
      • 演示事务对于delete和truncate的处理的区别:
      • 演示savepoint 的使用:
  • 视图
      • 视图的创建
      • 视图的修改
      • 视图的删除
      • 查看视图
      • 视图的更新
      • 视图练习
  • 总结

DML

简介

• DML(Data Manipulation Language –
数据操纵语言) 可以在下列条件下执行:
– 向表中插入数据
– 修改现存数据
– 删除现存数据
• 事务是由完成若干项工作的DML语句组成的

插入数据

INSERT 语句
• 使用 INSERT 语句向表中插入数据。
• 使用这种语法一次只能向表中插入一条数据。

INSERT INTO table [(column [, column...])]
VALUES (value [, value...]);

• 为每一列添加一个新值。
• 按列的默认顺序列出各个列的值。
• 在 INSERT 子句中随意列出列名和他们的值。
• 字符和日期型数据应包含在单引号中。
INSERT INTO t_mysql_departments(department_id, department_name, manager_id, location_id)
VALUES (70, 'Public Relations', 100, 1700);

INSERT INTO t_mysql_employees(employee_id,last_name,email,hire_date,job_id)
VALUES (300,’Tom’,’tom@126.com,to_date(2012-3-
21,’yyyy-mm-dd’),’SA_RAP’);

向表中插入空值

• 隐式方式: 在列名表中省略该列的值。
INSERT INTO t_mysql_departments (department_id, department_name )
VALUES (30, 'Purchasing');

显示方式: 在VALUES 子句中指定空值。
INSERT INTO t_mysql_departments
VALUES (100, 'Finance', NULL, NULL);

插入指定的值

INSERT INTO t_mysql_employees (employee_id, first_name, last_name, email, phone_number,hire_date, job_id, salary, commission_pct, manager_id,department_id)
VALUES (113, 'Louis', 'Popp', 'LPOPP', '515.124.4567', 
NOW(), 'AC_ACCOUNT', 6900, NULL, 205, 100);

从其它表中拷贝数据

• 在 INSERT 语句中加入子查询。
INSERT INTO emp2 
SELECT * 
FROM t_mysql_employees
WHERE department_id = 90;

INSERT INTO sales_reps(id, name, salary, commission_pct)
SELECT employee_id, last_name, salary, commission_pct
FROM t_mysql_employees
WHERE job_id LIKE '%REP%';

• 不必书写 VALUES 子句。

• 子查询中的值列表应与 INSERT 子句中的列名对应

更新数据

• 使用 UPDATE 语句更新数据。
UPDATE table
SET column = value [, column = value, ...]
[WHERE condition];

• 可以一次更新多条数据。
• 如果需要回滚数据,需要保证在DML前,进行
设置:SET AUTOCOMMIT = FALSE;

• 使用 WHERE 子句指定需要更新的数据。

一次修改多表的数据
案例:

#案例 1:修改张无忌的女朋友的手机号为114
UPDATE t_mysql_boys bo
INNER JOIN t_mysql_beauty b ON bo.`id`=b.`boyfriend_id`
SET b.`phone`='119',bo.`userCP`=1000
WHERE bo.`boyName`='张无忌';

#案例2:修改没有男朋友的女神的男朋友编号都为2号
UPDATE t_mysql_boys bo
RIGHT JOIN t_mysql_beauty b ON bo.`id`=b.`boyfriend_id`
SET b.`boyfriend_id`=2
WHERE bo.`id` IS NULL;

SELECT * FROM t_mysql_boys;

删除数据

使用 DELETE 语句从表中删除数据。
DELETE FROM table
[WHERE condition];

• 使用 WHERE 子句删除指定的记录。
DELETE FROM t_mysql_departments
WHERE department_name = 'Finance';

• 如果省略 WHERE 子句,则表中的全部数据将被删除
DELETE FROM copy_emp;

一次删除多表的数据

#案例:删除张无忌的女朋友的信息

DELETE b
FROM t_mysql_beauty b
INNER JOIN t_mysql_boys bo ON b.`boyfriend_id` = bo.`id`
WHERE bo.`boyName`='张无忌';


#案例:删除黄晓明的信息以及他女朋友的信息
DELETE b,bo
FROM t_mysql_beauty b
INNER JOIN t_mysql_boys bo ON b.`boyfriend_id`=bo.`id`
WHERE bo.`boyName`='黄晓明';

delete pk truncate
1.delete 可以加where 条件,truncate不能加
2.truncate删除,效率高一丢丢
3.假如要删除的表中有自增长列,
如果用delete删除后,再插入数据,自增长列的值从断点开始,
而truncate删除后,再插入数据,自增长列的值从1开始。
4.truncate删除没有返回值,delete删除有返回值
5.truncate删除不能回滚,delete删除可以回滚.

SELECT * FROM t_mysql_boys;

DELETE FROM t_mysql_boys;
TRUNCATE TABLE t_mysql_boys;
INSERT INTO t_mysql_boys (boyname,usercp)
VALUES('张飞',100),('刘备',100),('关云长',100);

综合练习

#1.	运行以下脚本创建表my_employees

USE myemployees;
CREATE TABLE my_employees(
	Id INT(10),
	First_name VARCHAR(10),
	Last_name VARCHAR(10),
	Userid VARCHAR(10),
	Salary DOUBLE(10,2)
);
CREATE TABLE users(
	id INT,
	userid VARCHAR(10),
	department_id INT

);
#2.	显示表my_employees的结构
DESC my_employees;

#3.	向my_employees表中插入下列数据
ID	FIRST_NAME	LAST_NAME	USERID	SALARY
1	patel		Ralph		Rpatel	895
2	Dancs		Betty		Bdancs	860
3	Biri		Ben		Bbiri	1100
4	Newman		Chad		Cnewman	750
5	Ropeburn	Audrey		Aropebur	1550

#方式一:
INSERT INTO my_employees
VALUES(1,'patel','Ralph','Rpatel',895),
(2,'Dancs','Betty','Bdancs',860),
(3,'Biri','Ben','Bbiri',1100),
(4,'Newman','Chad','Cnewman',750),
(5,'Ropeburn','Audrey','Aropebur',1550);
DELETE FROM my_employees;
#方式二:

INSERT INTO my_employees
SELECT 1,'patel','Ralph','Rpatel',895 UNION
SELECT 2,'Dancs','Betty','Bdancs',860 UNION
SELECT 3,'Biri','Ben','Bbiri',1100 UNION
SELECT 4,'Newman','Chad','Cnewman',750 UNION
SELECT 5,'Ropeburn','Audrey','Aropebur',1550;

				
#4.	 向users表中插入数据
1	Rpatel	10
2	Bdancs	10
3	Bbiri	20
4	Cnewman	30
5	Aropebur	40

INSERT INTO users
VALUES(1,'Rpatel',10),
(2,'Bdancs',10),
(3,'Bbiri',20);


#5.将3号员工的last_name修改为“drelxer”
UPDATE my_employees SET last_name='drelxer' WHERE id = 3;


#6.将所有工资少于900的员工的工资修改为1000
UPDATE my_employees SET salary=1000 WHERE salary<900;

#7.将userid 为Bbiri的user表和my_employees表的记录全部删除

DELETE u,e
FROM users u
JOIN my_employees e ON u.`userid`=e.`Userid`
WHERE u.`userid`='Bbiri';

#8.删除所有数据

DELETE FROM my_employees;
DELETE FROM users;
#9.检查所作的修正

SELECT * FROM my_employees;
SELECT * FROM users;

#10.清空表my_employees
TRUNCATE TABLE my_employees;

TCL(事务控制语言)

事务的特性:
ACID
原子性:一个事务不可再分割,要么都执行要么都不执行
一致性:一个事务执行会使数据从一个一致状态切换到另外一个一致状态
隔离性:一个事务的执行不受其他事务的干扰
持久性:一个事务一旦提交,则会永久的改变数据库的数据.

事务:
一个或一组sql语句组成一个执行单元,这个执行单元要么全部执行,要么全部不执行。

案例:转账

张三丰  1000
郭襄	1000

updateset 张三丰的余额=500 where name='张三丰'
意外
updateset 郭襄的余额=1500 where name='郭襄'

事务的创建

隐式事务:事务没有明显的开启和结束的标记
比如insertupdatedelete语句

delete fromwhere id =1;

显式事务:事务具有明显的开启和结束的标记
前提:必须先设置自动提交功能为禁用

set autocommit=0;

步骤1:开启事务
set autocommit=0;
start transaction;可选的
步骤2:编写事务中的sql语句(select insert update delete)
语句1;
语句2;
...

步骤3:结束事务
commit;提交事务
rollback;回滚事务

savepoint 节点名;设置保存点

开启事务的语句;

updateset 张三丰的余额=500 where name='张三丰'

updateset 郭襄的余额=1500 where name='郭襄' 

结束事务的语句;

SHOW VARIABLES LIKE 'autocommit';
SHOW ENGINES;

事务的隔离级别:

事务的隔离级别:
		  脏读		不可重复读	幻读
read uncommitted:√		√		√
read committed:  ×		√		√
repeatable read: ×		×		√
serializable	  ×     ×       ×


mysql中默认 第三个隔离级别 repeatable read
oracle中默认第二个隔离级别 read committed
查看隔离级别
select @@tx_isolation;
设置隔离级别
set session|global transaction isolation level 隔离级别;

演示事务的使用步骤:

#开启事务
SET autocommit=0;
START TRANSACTION;
#编写一组事务的语句
UPDATE account SET balance = 1000 WHERE username='张无忌';
UPDATE account SET balance = 1000 WHERE username='赵敏';

#结束事务
ROLLBACK;
#commit;

SELECT * FROM account;

演示事务对于delete和truncate的处理的区别:

SET autocommit=0;
START TRANSACTION;

DELETE FROM account;
ROLLBACK;

演示savepoint 的使用:

SET autocommit=0;
START TRANSACTION;
DELETE FROM account WHERE id=25;
SAVEPOINT a;#设置保存点
DELETE FROM account WHERE id=28;
ROLLBACK TO a;#回滚到保存点

SELECT * FROM account;

视图

含义:虚拟表,和普通表一样使用
mysql5.1版本出现的新特性,是通过表动态生成的数据

比如:舞蹈班和普通班级的对比
	    创建语法的关键字	是否实际占用物理空间	    使用

视图	create view		只是保存了sql逻辑	增删改查,只是一般不能增删改

表	    create table		保存了数据		增删改查

案例

#案例:查询姓张的学生名和专业名
SELECT stuname,majorname
FROM stuinfo s
INNER JOIN major m ON s.`majorid`= m.`id`
WHERE s.`stuname` LIKE '张%';

CREATE VIEW v1
AS
SELECT stuname,majorname
FROM stuinfo s
INNER JOIN major m ON s.`majorid`= m.`id`;

SELECT * FROM v1 WHERE stuname LIKE '张%';

视图的创建

语法:create view 视图名 as 查询语句;

USE myemployees;

#1.查询姓名中包含a字符的员工名、部门名和工种信息
#①创建
CREATE VIEW myv1
AS

SELECT last_name,department_name,job_title
FROM employees e
JOIN departments d ON e.department_id  = d.department_id
JOIN jobs j ON j.job_id  = e.job_id;


#②使用
SELECT * FROM myv1 WHERE last_name LIKE '%a%';






#2.查询各部门的平均工资级别

#①创建视图查看每个部门的平均工资
CREATE VIEW myv2
AS
SELECT AVG(salary) ag,department_id
FROM employees
GROUP BY department_id;

#②使用
SELECT myv2.`ag`,g.grade_level
FROM myv2
JOIN job_grades g
ON myv2.`ag` BETWEEN g.`lowest_sal` AND g.`highest_sal`;



#3.查询平均工资最低的部门信息

SELECT * FROM myv2 ORDER BY ag LIMIT 1;

#4.查询平均工资最低的部门名和工资

CREATE VIEW myv3
AS
SELECT * FROM myv2 ORDER BY ag LIMIT 1;


SELECT d.*,m.ag
FROM myv3 m
JOIN departments d
ON m.`department_id`=d.`department_id`;

视图的修改

语法1:create or replace view 视图名 as 查询语句;

SELECT * FROM myv3 

CREATE OR REPLACE VIEW myv3
AS
SELECT AVG(salary),job_id
FROM employees
GROUP BY job_id;

语法2:alter view 视图名 as 查询语句;

ALTER VIEW myv3
AS
SELECT * FROM employees;

视图的删除

语法:drop view 视图名,视图名,…;

语法:drop view 视图名,视图名,...;

查看视图

DESC myv3;

SHOW CREATE VIEW myv3;

视图的更新

CREATE OR REPLACE VIEW myv1
AS
SELECT last_name,email,salary*12*(1+IFNULL(commission_pct,0)) "annual salary"
FROM employees;

CREATE OR REPLACE VIEW myv1
AS
SELECT last_name,email
FROM employees;


SELECT * FROM myv1;
SELECT * FROM employees;
#1.插入

INSERT INTO myv1 VALUES('张飞','[email protected]');

#2.修改
UPDATE myv1 SET last_name = '张无忌' WHERE last_name='张飞';

#3.删除
DELETE FROM myv1 WHERE last_name = '张无忌';

#具备以下特点的视图不允许更新


#①包含以下关键字的sql语句:分组函数、distinct、group  by、having、union或者union all

CREATE OR REPLACE VIEW myv1
AS
SELECT MAX(salary) m,department_id
FROM employees
GROUP BY department_id;

SELECT * FROM myv1;

#更新
UPDATE myv1 SET m=9000 WHERE department_id=10;

#②常量视图
CREATE OR REPLACE VIEW myv2
AS

SELECT 'john' NAME;

SELECT * FROM myv2;

#更新
UPDATE myv2 SET NAME='lucy';





#③Select中包含子查询

CREATE OR REPLACE VIEW myv3
AS

SELECT department_id,(SELECT MAX(salary) FROM employees) 最高工资
FROM departments;

#更新
SELECT * FROM myv3;
UPDATE myv3 SET 最高工资=100000;


#④join
CREATE OR REPLACE VIEW myv4
AS

SELECT last_name,department_name
FROM employees e
JOIN departments d
ON e.department_id  = d.department_id;

#更新

SELECT * FROM myv4;
UPDATE myv4 SET last_name  = '张飞' WHERE last_name='Whalen';
INSERT INTO myv4 VALUES('陈真','xxxx');



#⑤from一个不能更新的视图
CREATE OR REPLACE VIEW myv5
AS

SELECT * FROM myv3;

#更新

SELECT * FROM myv5;

UPDATE myv5 SET 最高工资=10000 WHERE department_id=60;



#⑥where子句的子查询引用了from子句中的表

CREATE OR REPLACE VIEW myv6
AS

SELECT last_name,email,salary
FROM employees
WHERE employee_id IN(
	SELECT  manager_id
	FROM employees
	WHERE manager_id IS NOT NULL
);

#更新
SELECT * FROM myv6;
UPDATE myv6 SET salary=10000 WHERE last_name = 'k_ing';

视图练习

#一、创建视图emp_v1,要求查询电话号码以‘011’开头的员工姓名和工资、邮箱
CREATE OR REPLACE VIEW emp_v1
AS
SELECT last_name,salary,email
FROM employees
WHERE phone_number LIKE '011%';

#二、创建视图emp_v2,要求查询部门的最高工资高于12000的部门信息
CREATE OR REPLACE VIEW emp_v2
AS
SELECT MAX(salary) mx_dep,department_id
FROM employees
GROUP BY department_id
HAVING MAX(salary)>12000;


SELECT d.*,m.mx_dep
FROM departments d
JOIN emp_v2 m
ON m.department_id = d.`department_id`;

总结

内容有点多,希望能帮到大家!!

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