SQL 基本（Head First）

CREATE TABLE my_contacts
(
last_name VARCHAR(30),
first_name VARCHAR(30),
email VARCHAR(50),
gender CHAR(1),
birthday DATE,
profession VARCHAR(50),
location VARCHAR(50),
status VARCHAR(20),
interests VARCHAR(100),
seeking VARCHAR(100)
);

1. IS NULL

2. LIKE, 通配符：%任意数量字符；_一个字符

3. BETWEEN AND(等价于<=,>=)

4. NOT: 置于每个查询条件前，还有NOT IN/ NOT NULL

5. IN

DROP TABLE IF EXISTS drink_info;
CREATE TABLE drink_info
(
drink_name VARCHAR(20) NOT NULL,
cost DEC(2,1) NOT NULL,
carbs DEC(3,1) NOT NULL,
color VARCHAR(10) NOT NULL,
ice CHAR(1) NOT NULL,
calories int NOT NULL
);

INSERT INTO drink_info
VALUES
('Blackthorn',2,8.4,'yellow','y',33),
('Blue Moon',2.5,3.2,'blue','y',12),
('Oh My Gosh',3.5,8.6,'orahge','y',35),
('Lime Fizz',2.5,5.4,'green','y',171),
('Indian Summer',2.8,7.2,'brown','N',30),
('kiss',5.5,42.5,'burbe','y',171);

设计/创建 数据库表时，对象化事物，按需求找出原子操作。
数据库表规范化 - 1NF，第一范式
主键

SHOW CREATE TABLE 表名，用于拿到create table时的代sql

SHOW CREATE TABLE my_contacts;
SHOW COLUMNS FROM my_contacts;
SHOW CREATE DATABASE gregs_list;
SHOW INDEX FROM my_contacts;

CREATE TABLE onetable
(
id INT NOT NULL AUTO_INCREMENT,
first_name VARCHAR(20) NOT NULL,
second_name VARCHAR(20) NOT NULL,
PRIMARY KEY(id)
);

INSERT INTO onetable
VALUES
(NULL,'chris','chen');

INSERT INTO onetable
(first_name,second_name)
VALUES
('BOB', 'BARY');

INSERT INTO onetable
VALUES
(99,'BOB', 'BARY');

AUTO_INCREMENT会自动忽略NULL关键字

设计表时，遵循1NF(第一范式)：1. 数据原子性；2. 每行唯一标识（primary key）

ALTER TABLE my_contacts
ADD COLUMN id INT NOT NULL AUTO_INCREMENT FIRST,
ADD PRIMARY KEY(id);

ALTER TABLE my_contacts
ADD COLUMN phone_number CHAR(10);

默认将phone_number列添加到表的最后。

DROP TABLE IF EXISTS projekts;
CREATE TABLE projekts
(
number INT,
descriptionofproj VARCHAR(50),
contractoronjob VARCHAR(10)
);
INSERT INTO projekts
(descriptionofproj, contractoronjob)
VALUES
('outside house painting','Murphy'),
('kitchen remodel','Valdez'),
('wood floor installation','keller');

使用ALTER的Change，Modify，Add对原表进行修改。
1. 修改表名：rename to

ALTER TABLE projekts
RENAME TO project_list;

2. 改变列名及类型

ALTER TABLE project_list
CHANGE COLUMN number proj_id INT NOT NULL AUTO_INCREMENT,
ADD PRIMARY KEY (proj_id);

3. 同时改变多列的名称和类型

ALTER TABLE project_list
CHANGE COLUMN descriptionofproj proj_desc VARCHAR(100),
CHANGE COLUMN contractoronjob con_name VARCHAR(30);
4. 只改变列的类型，使用Modify

ALTER TABLE project_list
MODIFY proj_desc VARCHAR(120);

5. 同时增加多列

ALTER TABLE project_list
ADD COLUMN phone VARCHAR(20) NOT NULL,
ADD COLUMN start_date DATE NOT NULL,
ADD COLUMN price DEC(10,2) NOT NULL;

6. 删除某列

ALTER TABLE project_list
DROP COLUMN start_date;

7. ALTER练习

DROP TABLE IF EXISTS hooptie;
CREATE TABLE hooptie
(
color VARCHAR(10),
year CHAR(4),
make VARCHAR(10),
mo VARCHAR(10),
howmuch DEC(9,3)
);

INSERT INTO hooptie
VALUES
('silver','1998','Porsche','Boxter',17992.540),
('red','2002','Cadillac','Escalade',40215.9);

INSERT INTO hooptie
(year,make,mo,howmuch)
VALUES
('2000','Jaguar','XJ',15995);

ALTER TABLE hooptie
ADD COLUMN car_id INT NOT NULL AUTO_INCREMENT FIRST,
ADD COLUMN VIN VARCHAR(20) NOT NULL AFTER car_id,
ADD PRIMARY KEY(car_id);

UPDATE hooptie
SET VIN = 'RNKLK66N33G213481'
WHERE car_id = 1;

UPDATE hooptie
SET VIN = 'SAEDA44B175BO4113'
WHERE car_id = 2;

UPDATE hooptie
SET VIN = '3GYEK63NT2G280668'
WHERE car_id = 3;

DROP TABLE IF EXISTS cookie_sales;
CREATE TABLE cookie_sales
(
ID INT NOT NULL AUTO_INCREMENT,
first_name VARCHAR(15) NOT NULL,
sales DEC(4,2),
sale_date DATE,
PRIMARY KEY(ID)
);

INSERT INTO cookie_sales
(first_name, sales, sale_date)
VALUES
('Lindsay', 32.02, '2007-03-06'),
('Paris', 26.53, '2007-03-06'),
('Britney', 11.25, '2007-03-06'),
('Nicole', 18.96, '2007-03-06'),
('Lindsay', 9.16, '2007-03-07');

INSERT INTO cookie_sales
(first_name, sales, sale_date)
VALUES
('Britney', 11.75, '2007-03-06');

SELECT SUM(sales) FROM cookie_sales WHERE first_name = 'Britney';

SELECT first_name, SUM(sales) FROM cookie_sales
GROUP BY first_name
ORDER BY SUM(sales) DESC;

SELECT DISTINCT sale_date
FROM cookie_sales
ORDER BY sale_date DESC
LIMIT 1;

SELECT first_name, SUM(sales)
FROM cookie_sales
GROUP BY first_name
ORDER BY SUM(sales) DESC
LIMIT 1,1;

LIMIT：从0开始计数 

同select搭配的有：DISTINCT,SUM.AVG,MAX,MIN,COUNT,GROUP BY, ORDER BY,LIMIT

外键：

CREATE TABLE interests
(
int_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
interest VARCHAR(50) NOT NULL,
contact_id INT NOT NULL,
CONSTRAINT my_contacts_contact_id_fk
FOREIGN KEY(contact_id)
REFERENCES my_contacts(contact_id)
);

 所谓的 Schema 指数据库设计模式（一对一，多对一，多对多），表之间的关系，列之间的关系等。

一对一：很少用; 一对多和多对多常用

组合主键：

CREATE TABLE super_heroes
(
name VARCHAR(20) NOT NULL,
power VARCHAR(25) NOT NULL,
weakness VARCHAR(20)
);

INSERT INTO super_heroes

VALUES
('Super Trashman','Cleans quickly','bleach'),
('Super Guy','Flies','birds'),
('Wonder Waiter','Never forgets an order','insects');

INSERT INTO super_heroes
(name, power)
VALUES
('The Broker','Makesmoneyfromnothing');

 
函数依赖：T.x -> T.y 表T的y列依赖于x列的改变

传递函数依赖：某个非键列与另一个非键列有关联

Exercise:

ALTER TABLE my_contacts
ADD COLUMN interest1 VARCHAR(50),
ADD COLUMN interest2 VARCHAR(50),
ADD COLUMN interest3 VARCHAR(50);

UPDATE my_contacts
SET interest1 = TRIM(SUBSTRING_INDEX(interests,',',1));
UPDATE my_contacts
SET interest2 = TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(interests,',',2),',',-1));
UPDATE my_contacts
SET interest3 = TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(interests,',',3),',',-1));
-- ineterests to interest4
UPDATE my_contacts
SET interests = TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(interests,',',4),',',-1));

ALTER TABLE my_contacts
CHANGE COLUMN interests interest4 VARCHAR(100);

-- 1. create / insert / select
CREATE TABLE profession
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
profession VARCHAR(50)
);

INSERT INTO profession (profession)
SELECT profession FROM my_contacts
GROUP BY profession ORDER BY profession;

DROP TABLE profession;

-- 2. create / select

CREATE TABLE profession AS SELECT profession FROM my_contacts
GROUP BY profession ORDER BY profession;

ALTER TABLE profession
ADD COLUMN id INT NOT NULL AUTO_INCREMENT FIRST,
ADD PRIMARY KEY (id);

-- 3. create / select
CREATE TABLE profession
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
profession VARCHAR(50)
) AS SELECT profession FROM my_contacts GROUP BY profession ORDER BY profession;

SELECT profession FROM my_contacts GROUP BY profession ORDER BY profession;
SELECT profession AS mc_prof FROM my_contacts GROUP BY mc_prof ORDER BY mc_prof;

内联接（Inner Join）：使用条件的联接

自然连接（Natural Join）是内联接的一种，连接列名相同的。
相等联接/不等联接：内联接的两种。

交叉联接(Cross Join)：也就是笛卡尔积联接

1. 交叉联接，关联子查询的速度慢；
2. 联接比子查询更有效率。

所谓的非关联子查询：指子查询能够单独运行

所谓的关联子查询：指子查询依赖外层查询

外联接：
1. 左外联接（Left Outer Join）
2. 右外联接（Right Ourter Join）

自联接
联合（Union）规则：
1. 查询的列数，类型一致
2. 查询顺序不影响结果
3. Union默认除去重复值，若保留重复值则使用Union All

检查约束，Check
1. 关键字CHECK设置列的约束条件
2. 语法： CHECK(类似where条件)
3. MySQL忽略CHECK约束，一般会用trigger代替
4.

-- ALTER TABLE my_contacts
-- ADD CONSTRAINT CHECK(gender in ('M','F'));

视图（View）：
1. 创建视图：

CREATE VIEW my_view AS
SELECT first_name, last_name FROM my_contacts;
2. 视图实际上就是一种虚拟表，也可以理解为是后续select的逻辑名称。
3. 使用View时，可以类似表一样使用
4. View不会在内存中一直存在，可用来简化查询。可以用drop view删除视图。
5. 对MySQL来说，可以利用View加上Check Option。

事务管理： 

CREATE TABLE `piggy_bank` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`coin` char(1) NOT NULL,
`coin_year` char(4) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8

START TRANSACTION;
SELECT * FROM piggy_bank;
UPDATE piggy_bank
SET coin = 'Q'
WHERE coin='P';
SELECT * FROM piggy_bank;
ROLLBACK;
SELECT * FROM piggy_bank;

START TRANSACTION;
SELECT * FROM piggy_bank;
UPDATE piggy_bank
SET coin = 'Q'
WHERE coin='P';
SELECT * FROM piggy_bank;
COMMIT;
SELECT * FROM piggy_bank;

权限管理：

1. 创建用户

CREATE USER 'chris'@'localhost' IDENTIFIED BY 'chen';
2. 利用Grant授予权限

GRANT SELECT ON my_contacts TO chris WITH GRANT OPTION;
3. 利用Revoke撤销权限

REVOKE SELECT ON my_contacts FROM chris; 有连带作用

REVOKE SELECT ON my_contacts FROM chris CASCADE;  有连带作用

REVOKE SELECT ON my_contacts FROM chris RESTRICT;  禁止连带作用

4. 角色：

CREATE ROLE data_entry;
GRANT SELECT ON my_contacts TO data_entry;
-----
GRANT data_entry TO chris;

REVOKE FROM/GRANT TO