<<SQL必知必会>> -- 笔记2

按照书的指南，选用MySQL作为DBMS，在使用例句之前需要先创建表
在官网下载的脚本在MAC上运行有报ASC字符的错，新建文件复制后解决
以下是去掉注释的SQL脚本
百度网盘链接
密码:okgi

检索数据

SELECT

单列

   SELECT prod_name
   FROM Products;

多列

   SELECT prod_id, prod_name, prod_price
   FROM Products;

所有列

通配符*

   SELECT *
   FROM Products;

检索不同的值

如果结果有相同的值，只出现一次

   SELECT DISTINCT vend_id
   FROM Products;

限制检索结果

返回不超过X行的结果

   SELECT prod_name 
   FROM Products 
   LIMIT 5 OFFSET 5;

后面的5表示从第五行算起
上述也可以写成

   SELECT prod_name 
   FROM Products 
   LIMIT 5,5;

三种注释

--，#，/**/

排序检索结果

ORDER BY

排序

  SELECT prod_name
  FROM Products
  ORDER BY prod_name;

按多个列排序

  SELECT prod_id, prod_price, prod_name 
  FROM Products 
  ORDER BY prod_price, prod_name;

按列的位置排序

  SELECT prod_id, prod_price, prod_name 
  FROM Products 
  ORDER BY 2,3;

指定排序方向

ASC或DESC，默认升序

  SELECT prod_id, prod_price, prod_name 
  FROM Products 
  ORDER BY prod_price DESC;

过滤数据

WHERE

单个值

  SELECT prod_name, prod_price
  FROM Products 
  WHERE prod_price = 3.49;

不匹配

  SELECT prod_name, prod_price
  FROM Products 
  WHERE prod_price <> 'DLLO1';

范围值

  SELECT prod_name, prod_price
  FROM Products 
  WHERE prod_price BETWEEN 5 AND 10;

空值

  SELECT cust_name
  FROM CuStomers
  WHERE cust_email IS NULL;

高级数据过滤

组合WHERE

AND

  SELECT prod_id, prod_price, prod_name
  FROM Products
  WHERE vend_id = 'DLL01' AND prod_price <= 4;

OR

  SELECT prod_name, prod_price 
  FROM Products 
  WHERE vend_id = 'DLL01' OR vend_id = 'BRS01';

AND的优先级高于OR，必要时用括号确定优先级

  SELECT prod_name, prod_price 
  FROM Products
  WHERE (vend_id = 'DLL01' OR vend_id = 'BRS01')
  AND prod_price >= 10;

IN

  SELECT prod_name, prod_price 
  FROM Products 
  WHERE vend_id IN ( 'DLL01', 'BRS01' )
  ORDER BY prod_name;

NOT

  SELECT prod_name 
  FROM Products 
  WHERE NOT vend_id = 'DLL01'
  ORDER BY prod_name DESC;

通配符

LIKE

%通配符

表示任何字符出现任意次数，包括0次

  SELECT prod_id, prod_name 
  FROM Products 
  WHERE prod_name LIKE 'Fish%';

_通配符

匹配任意单个字符

  SELECT prod_id, prod_name 
  FROM Products 
  WHERE prod_name LIKE '__ inch teddy bear';

[]通配符

指定一个字符集
在MySQL 8中使用似乎没有用，使用RLIKE和REGEXP和方括号都没用
建议查看手册，关于正则表达式部分

  SELECT cust_contact
  FROM Customers 
  WHERE cust_contact regexp 'J%'
  ORDER BY cust_contact;
-- after test, the '[]' is useless