我的SQL学习

目录

• 1.SQL基础
• 2.检索数据
• 3.排序检索数据
• 4.过滤数据
• 5.高级过滤
• 6.通配符过滤
• 7.创建计算字段
• 8.函数特性
• 9.函数
• 10.汇总数据
• 11.分组数据
• 12.子查询
• 13.联结
• 14.高级联结
• 15.组合查询
• 16.插入数据

SQL的学习之路，主要参考资料是：

SQL必知必会
W3school的SQL简介

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右击，新标签页即可打开原图

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操作使用的数据库为Access及MySQL。

数据采用的是SQL必知必会中的数据

（最下方可以下载数据）。其有5个表，表的关系如下：

表的关系

这里补充下，MySQL创建该数据库（2017.5.17）,复制到MySQL创建执行创建即可（数据来源于《SQL必知必会》）；

-- ----------------------
-- Create Customers table
-- ----------------------
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);

插入数据

-- ------------------------
-- Populate Customers table
-- ------------------------
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, '2012-05-01', '1000000001');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20006, '2012-01-12', '1000000003');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20007, '2012-01-30', '1000000004');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20008, '2012-02-03', '1000000005');
INSERT INTO Orders(order_num, order_date, cust_id)
VALUES(20009, '2012-02-08', '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);

1.SQL基础

基础

2.检索数据

检索数据

3.排序检索数据

排序检索数据

4.过滤数据

过滤数据

5.高级过滤

高级过滤

6.通配符过滤

通配符过滤

7.创建计算字段

创建计算字段

8.函数特性

函数特性

9.函数

函数

10.汇总数据

汇总数据

11.分组数据

分组数据

---

以上测试均在Access数据库中进行，以下于MySQL中进行，通过workbench（版本6.3）操作。

---

12.子查询

这里说白了就是select语句嵌套，如select * from （select cust_name from customers）

子查询

13.联结

笛卡尔积

联结

14.高级联结

高级联结

如果3个以上的表，那怎样联结？

1. 3个

 use test;
 select cust_name,cust_contact
 from (customers 
 inner join orders
 on customers.cust_id = orders.cust_id)
 inner join orderitems 
 on orderitems.order_num = orders.order_num;```

 语法可以概括为：

***`FROM (表1 INNER JOIN 表2 ON 表1.字段号=表2.字段号) INNER JOIN 表3 ON 表1.字段号=表3.字段号`***

2. 同理，4个表可以概括为：

***`FROM ((表1 INNER JOIN 表2 ON 表1.字段号=表2.字段号) INNER JOIN 表3 ON 表1.字段号=表3.字段号) INNER JOIN 表4 ON Member.字段号=表4.字段号`***


## 15.组合查询

![组合查询](http://upload-images.jianshu.io/upload_images/2151277-2f00deb32b8b47bb.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

****
 *如果代码块阅读困难，可移步[博客园](http://www.cnblogs.com/sunshinewang/p/6789419.html)*
****

***关于规则中列顺序，前后必须一致。***否则会出现如下情况：

```SQL
 1 use test; 
 2 select cust_name ,cust_email,cust_contact
 3 from customers
 4 where cust_state in ('IL','IN','MI')
 5 union all
 6 select cust_name,cust_contact,cust_email
 7 from customers
 8 where cust_name = 'Fun4All'```


 
返回结果为：

![返回结果](http://upload-images.jianshu.io/upload_images/2151277-8056401714986ffe.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

列的顺序一致，才会返回正确结果

```SQL
 1 use test;
 2 select cust_name ,cust_email,cust_contact
 3 from customers
 4 where cust_state in ('IL','IN','MI')
 5 union all
 6 select cust_name,cust_email,cust_contact
 7 from customers8 where cust_name = 'Fun4All'```

 
结果：

![返回结果](http://upload-images.jianshu.io/upload_images/2151277-322eef5f933e81f2.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

## 16.插入数据

***INSERT SELECT:***

它可以将SELCET语句结果插入表中，在***某种意义上可以完成表的复制***。
如：

```SQL
 1 USE test;#使用数据库test 
 2 CREATE TABLE CustNew 
 3 ( 
 4 cust_id  char(10)   NOT NULL ,
 5 cust_name  char(50)   NOT NULL ,
 6 cust_address  char(50)  NULL , 
 7 cust_city  char(50)  NULL ,
 8 cust_state  char(5)  NULL , 
 9 cust_zip  char(10)  NULL ,
10 cust_country  char(50)  NULL ,
11 cust_contact  char(50)  NULL ,
12 cust_email  char(255)  NULL 
13 );#创新新表 
14 INSERT INTO CustNew
15 (
16 cust_id,
17 cust_name,
18 cust_address,
19 cust_city,
20 cust_state,
21 cust_zip,
22 cust_country,
23 cust_contact,
24 cust_email
25 )
26 SELECT 
27 cust_id,
28 cust_name,
29 cust_address,
30 cust_city,
31 cust_state,
32 cust_zip,
33 cust_country,
34 cust_contact,
35 cust_email
36 FROM customers;#将customers表的数据插入新表alter
37 SELECT * FROM CustNew;```

返回结果如下：
 ![结果](http://upload-images.jianshu.io/upload_images/2151277-96aaf2720fa79e88.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
 
 而如果反过来用，大概就是：

```SQL
 1 insert into
 2 customers 
 3 （列1，列2，......）
 4 select
 5 列1，列2，.....
 6 from custnew```

 
即可完成将表custnew中的数据全部插入customers，这也完成了一条insert插入多条数据。

***通常，一条INSERT 语句，只能插入一行数据，要插入多行，就必须执行多个INSERT，但是， INSERT SELECT 是个例外。***

以上方法的复制，实际上是重新在数据库中创建了一个新表。

***SELECT INTO：***

这种方法，可以在SQL语句运行中创建一个表，并将一个表复制到这个全新的表。

***我们可以在实验新的SQL语句前，用其进行复制，这样就不影响到实际数据。***
如：

```SQL
 USE test;#使用数据库
 CREATE TABLE Cucopy as
 SELECT * FROM customers;#复制
 SELECT * FROM Cucopy;```

 返回结果，与上表一致。
 
![插入](http://upload-images.jianshu.io/upload_images/2151277-45f6e82846597d13.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

## 17.更新和删除

![更新和删除](http://upload-images.jianshu.io/upload_images/2151277-c9a8f39f57480ec5.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
 
 
## 18.创建和操纵表

这里中点说一下创建表时，指定默认值的问题。一般来说，创建表时，我们需要指定列的数据类型、是否NULL列。关于NULL值具体说明请看下图。

默认值要是用的好，可以省却我们很多时间。

因其经常用于指定默认日期，这里以日期为例。

首先，在MySQL中内建的日期函数：

|函数|描述|
|-----|--|
|[NOW()](http://www.w3school.com.cn/sql/func_now.asp)|返回当前的日期和时间|
|[CURDATE()](http://www.w3school.com.cn/sql/func_curdate.asp)|返回当前的日期|
|[CURTIME()](http://www.w3school.com.cn/sql/func_curtime.asp)|返回当前的时间|
|[DATE()](http://www.w3school.com.cn/sql/func_date.asp)|提取日期或日期/时间表达式的日期部分|
|[EXTRACT()](http://www.w3school.com.cn/sql/func_extract.asp)|返回日期/时间按的单独部分|
|[DATE_ADD()](http://www.w3school.com.cn/sql/func_date_add.asp)|给日期添加指定的时间间隔|
|[DATE_SUB()](http://www.w3school.com.cn/sql/func_date_sub.asp)|从日期减去指定的时间间隔|
|[DATEDIFF()](http://www.w3school.com.cn/sql/func_datediff_mysql.asp)|返回两个日期之间的天数|
|[DATE_FORMAT()](http://www.w3school.com.cn/sql/func_date_format.asp)|用不同的格式显示日期/时间|

 
创建数据库t2,插入表。如下：

```SQL
 CREATE DATABASE t2;
 USE t2;
 CREATE TABLE test
 (
 id int(5) NOT NULL,noedate timestamp NOT NULL DEFAULT 
 current_timestamp()
 );```

调用如下：

```SQL
 USE t2;
 INSERT INTO test(id)values(1);
 SELET * FROM test;```

返回结果：

![返回结果](http://upload-images.jianshu.io/upload_images/2151277-06833413f120003a.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

以下SQL不合法：

- `time_d time NOT NULL DEFAULT CURTIME(), `
- `date_e date NOT NULL DEFAULT CURDATE(),`
- `datetime_f datetime NOT NULL DEFAULT NOW(),` 

 
- DATETIME类型：NOW()函数以'YYYY-MM-DD HH:MM:SS'返回当前的日期时间，可以直接存到DATETIME字段中。不支持使用系统默认值。 
- DATE类型：CURDATE()以'YYYY-MM-DD'的格式返回今天的日期，可以直接存到DATE字段中。不支持使用系统默认值。 
- TIME类型：CURTIME()以'HH:MM:SS'的格式返回当前的时间，可以直接存到TIME字段中。不支持使用系统默认值。 
常见错误：

```SQL
CREATE TABLE dnt_forums
(
 aa int NOT NULL DEFAULT (''), 
 bb date NOT NULL DEFAULT (getdate()), 
 cc char(50) NOT NULL DEFAULT (null) 
）；```

 
+ aa 是 int 类型，默认值也得是整型，并且default后边不要（）括号 。
+ bb date类型不支持使用系统默认值，改成timestamp，能过now()取系统时间 。
+ cc 已经不允许为空（not null）所以不能默认为 null ，可以改成空字符串 。
修改：

```SQL
 CREATE TABLE dnt_forums
 (
  aa int NOT NULL DEFAULT 2,
 bb timestamp NOT NULL DEFAULT now(),
 cc char(50) NOT NULL DEFAULT ''
 ); ```

 
这个日期问题，依然有很多不太明白的地方，以后学习过程碰到继续解决。
主要参考：

[脚本之家](http://www.jb51.net/article/33570.htm)、[博客](http://blog.csdn.net/justdb/article/details/7965490)

![创建和操纵表](http://upload-images.jianshu.io/upload_images/2151277-3e42c57a43b77707.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

重命名表：

`RENAME TABLE cucopy1 TO hi;`

 
 删除表：

`DROP TABLE hi;`

*待续*