目录
说明：本文是对sql必知必会（第五版）的学习总结，具体使用的数据库是mysql.
这篇文章中主要对mysql的基础知识，用户相关命令，创建，更新，删除表等进行总结。
一：mysql的基础知识
1）数据库(database): 保存有组织的数据库。
2）表(table) : 特定类型的数据结果化清单。
存储在表中的数据是一种类型的数据或者一个清单的数据
3）主键(primary key):
表中每一行都应该有可以唯一标识自己的列，一列中唯一能够识别表中的每一行的值。
在设计表是应该总是设计带有主键，设置为主键瞒着的条件为：
- 任意两行都不具有相同的主键值
- 每个行都必须带有主键值（主键值列不允许为null）
- 主键列中的值不允许修改更新
- 主键值不能重用。
二：mysql用户有关命令
1）进入数据库：
mysql -u root -p
接着按照提示输入密码即可登陆成功2）修改mysql密码
$ mysql -u root
mysql> USE mysql;
mysql> UPDATE user SET authentication_string=PASSWORD("NEWPASSWORD") WHERE User='root';3）创建，查询，删除用户
// 创建
mysql> CREATE USER 'test1'@'localhost' identified by '1234567';
Query OK, 0 rows affected (0.00 sec)
//查询
mysql> SELECT USER FROM mysql.user; 查询所有用户
mysql> SHOW GRANTS For [email protected]'localhost'; 查询具体某个用户
//删除
mysql> DROP USER 'test1'@'localhost';
Query OK, 0 rows affected (0.01 sec)三：创建更新删除数据表
3.1 创建表
可以使用交互式工具进行操作，这儿主要讲解使用mysql语句进行创建
利用 create table 表名 来创建表
需以下信息：
- 新表的名字，在关键字CREATE TABLE之后
- 表列的名字和定义，用逗号隔开。
- 该列是否可为null
3.2 创建《SQL必知必会》本书所需要的所有数据表
CREATE TABLE Customers
(
cust_id char(10) NOT NULL ,
cust_name char(50) NOT NULL ,
cust_address char(50) NULL ,
cust_city char(50) NULL ,
cust_state char(5) NULL ,
cust_zip char(10) NULL ,
cust_country char(50) NULL ,
cust_contact char(50) NULL ,
cust_email char(255) NULL
);
-- -----------------------
-- Create OrderItems table
-- -----------------------
CREATE TABLE OrderItems
(
order_num int NOT NULL ,
order_item int NOT NULL ,
prod_id char(10) NOT NULL ,
quantity int NOT NULL ,
item_price decimal(8,2) NOT NULL
);
-- -------------------
-- Create Orders table
-- -------------------
CREATE TABLE Orders
(
order_num int NOT NULL ,
order_date datetime NOT NULL ,
cust_id char(10) NOT NULL
);
-- ---------------------
-- Create Products table
-- ---------------------
CREATE TABLE Products
(
prod_id char(10) NOT NULL ,
vend_id char(10) NOT NULL ,
prod_name char(255) NOT NULL ,
prod_price decimal(8,2) NOT NULL ,
prod_desc text NULL
);
-- --------------------
-- Create Vendors table
-- --------------------
CREATE TABLE Vendors
(
vend_id char(10) NOT NULL ,
vend_name char(50) NOT NULL ,
vend_address char(50) NULL ,
vend_city char(50) NULL ,
vend_state char(5) NULL ,
vend_zip char(10) NULL ,
vend_country char(50) NULL
);
-- -------------------
-- Define primary keys
-- -------------------
ALTER TABLE Customers ADD PRIMARY KEY (cust_id);
ALTER TABLE OrderItems ADD PRIMARY KEY (order_num, order_item);
ALTER TABLE Orders ADD PRIMARY KEY (order_num);
ALTER TABLE Products ADD PRIMARY KEY (prod_id);
ALTER TABLE Vendors ADD PRIMARY KEY (vend_id);
-- -------------------
-- Define foreign keys
-- -------------------
ALTER TABLE OrderItems ADD CONSTRAINT FK_OrderItems_Orders FOREIGN KEY (order_num) REFERENCES Orders (order_num);
ALTER TABLE OrderItems ADD CONSTRAINT FK_OrderItems_Products FOREIGN KEY (prod_id) REFERENCES Products (prod_id);
ALTER TABLE Orders ADD CONSTRAINT FK_Orders_Customers FOREIGN KEY (cust_id) REFERENCES Customers (cust_id);
ALTER TABLE Products ADD CONSTRAINT FK_Products_Vendors FOREIGN KEY (vend_id) REFERENCES Vendors (vend_id);
格式：
create table name{
列名一 数据类型 是否可为null
列名一 数据类型 是否可为null
}
[ 注意]：只有不允许null的值的列可作为主键，允许null值的列不能作为唯一标识。
3.2 更新表
使用 ALTER TABLE 语句来更新内容，但有几个地方要注意
- 表中包含数据是不用对其进行更新。
- 所有的DBMS都允许表添加列
- 许多DBMS不允许删除更新列
- ALTER TABLE 之后给出要更改的表面。
- 所做更改的列表
#给Vendors 表添加一个列，数据类型为CHAR
ALTER TABLE Vendors
ADD vend_phone CHAR(20);# 把Vendors表的vend_phone列删除
ALTER TABLE Vendors
DROP COLUMN vend_phone;3.3 删除表
drop table + 表名
DROP TABLE CustCopy;四.插入更新删除数据
4.1数据插入
使用insert into ...... values 语句进行数据插入
insert用来插入(添加)行到数据库，对应有下面三种情况。
- 插入完整的行
- 插入行的一部分
- 插入某些查询结果
1）插入完整的行
# 编写依赖与特定列次序的SQL语句，这样做有时会出错，但编写方便。
INSERT INTO Customers
VALUES('1000000006',
'Toy Land',
'123 Any Street',
'New York',
'NY',
'11111',
'USA',
NULL,
NULL);上面方法一般不推荐使用，我们一般使用指定顺序插入数据，即指定列名，指定数据
INSERT INTO Customers(cust_id,
cust_contact,
cust_email,
cust_name,
cust_address,
cust_city,
cust_state,
cust_zip)
VALUES('1000000009',
NULL,
NULL,
'Toy Land',
'123 Any Street',
'New York',
'NY',
'11111');2）插入部分行
指定某列提供值，其他的不提供值。
INSERT INTO Customers(cust_id,
cust_contact,
cust_email,
cust_name,
cust_address,
)
VALUES('1000000009',
NULL,
NULL,
'Toy Land',
'123 Any Street'
);3）插入某些查询结果
INSERT INTO CustomersNew(cust_id,
cust_contact,
cust_email,
cust_name,
cust_address,
cust_city,
cust_state,
cust_zip,
cust_country)
SELECT cust_id,
cust_contact,
cust_email,
cust_name,
cust_address,
cust_city,
cust_state,
cust_zip,
cust_country
FROM Customers;作用：将CustomersNew所有的数据导入Customers
【注意】：没有使用values关键字
补充：此处将我们后面需要用到的Customers,Orders,ItemOrders，vendors,Products插入数据的代码呈现出来
INSERT INTO Customers(cust_id, cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country, cust_contact, cust_email)
VALUES('1000000001', 'Village Toys', '200 Maple Lane', 'Detroit', 'MI', '44444', 'USA', 'John Smith', '[email protected]');
INSERT INTO Customers(cust_id, cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country, cust_contact)
VALUES('1000000002', 'Kids Place', '333 South Lake Drive', 'Columbus', 'OH', '43333', 'USA', 'Michelle Green');
INSERT INTO Customers(cust_id, cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country, cust_contact, cust_email)
VALUES('1000000003', 'Fun4All', '1 Sunny Place', 'Muncie', 'IN', '42222', 'USA', 'Jim Jones', '[email protected]');
INSERT INTO Customers(cust_id, cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country, cust_contact, cust_email)
VALUES('1000000004', 'Fun4All', '829 Riverside Drive', 'Phoenix', 'AZ', '88888', 'USA', 'Denise L. Stephens', '[email protected]');
INSERT INTO Customers(cust_id, cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country, cust_contact)
VALUES('1000000005', 'The Toy Store', '4545 53rd Street', 'Chicago', 'IL', '54545', 'USA', 'Kim Howard');
-- ----------------------
-- Populate Vendors table
-- ----------------------
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('BRS01','Bears R Us','123 Main Street','Bear Town','MI','44444', 'USA');
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('BRE02','Bear Emporium','500 Park Street','Anytown','OH','44333', 'USA');
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('DLL01','Doll House Inc.','555 High Street','Dollsville','CA','99999', 'USA');
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('FRB01','Furball Inc.','1000 5th Avenue','New York','NY','11111', 'USA');
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('FNG01','Fun and Games','42 Galaxy Road','London', NULL,'N16 6PS', 'England');
INSERT INTO Vendors(vend_id, vend_name, vend_address, vend_city, vend_state, vend_zip, vend_country)
VALUES('JTS01','Jouets et ours','1 Rue Amusement','Paris', NULL,'45678', 'France');
-- -----------------------
-- Populate Products table
-- -----------------------
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BR01', 'BRS01', '8 inch teddy bear', 5.99, '8 inch teddy bear, comes with cap and jacket');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BR02', 'BRS01', '12 inch teddy bear', 8.99, '12 inch teddy bear, comes with cap and jacket');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BR03', 'BRS01', '18 inch teddy bear', 11.99, '18 inch teddy bear, comes with cap and jacket');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BNBG01', 'DLL01', 'Fish bean bag toy', 3.49, 'Fish bean bag toy, complete with bean bag worms with which to feed it');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BNBG02', 'DLL01', 'Bird bean bag toy', 3.49, 'Bird bean bag toy, eggs are not included');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('BNBG03', 'DLL01', 'Rabbit bean bag toy', 3.49, 'Rabbit bean bag toy, comes with bean bag carrots');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('RGAN01', 'DLL01', 'Raggedy Ann', 4.99, '18 inch Raggedy Ann doll');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('RYL01', 'FNG01', 'King doll', 9.49, '12 inch king doll with royal garments and crown');
INSERT INTO Products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('RYL02', 'FNG01', 'Queen doll', 9.49, '12 inch queen doll with royal garments and crown');
-- ---------------------
-- Populate Orders table
-- ---------------------
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20005, '2020-05-01', '1000000001');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20006, '2020-01-12', '1000000003');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20007, '2020-01-30', '1000000004');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20008, '2020-02-03', '1000000005');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20009, '2020-02-08', '1000000001');
-- -------------------------
-- Populate OrderItems table
-- -------------------------
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20005, 1, 'BR01', 100, 5.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20005, 2, 'BR03', 100, 10.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20006, 1, 'BR01', 20, 5.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20006, 2, 'BR02', 10, 8.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20006, 3, 'BR03', 10, 11.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20007, 1, 'BR03', 50, 11.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20007, 2, 'BNBG01', 100, 2.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20007, 3, 'BNBG02', 100, 2.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20007, 4, 'BNBG03', 100, 2.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20007, 5, 'RGAN01', 50, 4.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20008, 1, 'RGAN01', 5, 4.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20008, 2, 'BR03', 5, 11.99);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20008, 3, 'BNBG01', 10, 3.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20008, 4, 'BNBG02', 10, 3.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20008, 5, 'BNBG03', 10, 3.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20009, 1, 'BNBG01', 250, 2.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20009, 2, 'BNBG02', 250, 2.49);
INSERT INTO OrderItems(order_num, order_item, prod_id, quantity, item_price)
VALUES(20009, 3, 'BNBG03', 250, 2.49);
4.2 更新数据
使用update....set语句
UPDATE Customers
SET cust_email = '[email protected]'
WHERE cust_id = '1000000005';4.3 删除数据
DELETE FROM Customers
WHERE cust_id = '1000000009';用于删除表中指定的数据
补充：更新和删除的原则
- UPDATE跟DELETE语句都具有WHERE子句，如果忽略WHERE子句建会应用到所有行，所以除非更新所有行
- 保证每个表都有主键，WHERE应用到主键。
- 使用UPDATE和DELETE语句前先，先SELECT进行测试，确保编写的WHERE子句正确。
- 使用强制实施引用完整性数据库，防止误删除行。
- 现在MYSQL不带有WHERE子句的UPDATE或DELETE子句执行。