《MySQL必知必会》第六七章-过滤数据与数据过滤

WHERE子句：
SELECT prod_name, prod_price
FROM Products
WHERE prod_price = 3.49;

SELECT vend_id, prod_name
FROM Products
WHERE vend_id <> 'DLL01';

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

空值检查：
SELECT cust_name
FROM Customers
WHERE cust_email IS NULL;

操作符（operator）：

用来联结或改变WHERE子句中的子句的关键字，也成为逻辑操作符。

AND操作符：

SELECT prod_id, prod_price, prod_name

FROM Products

WHERE vend_id = 'DLL01' AND prod_price <= 4;

OR操作符：

SELECT vend_id, prod_name, prod_price

FROM Products

WHERE vend_id = 'DLL01' OR vend_id = 'BR501';

求值顺序：

SELECT vend_id, prod_name, prod_price

FROM Products

WHERE (vend_id = 'DLL01' OR vend_id = 'BRS01')

                AND prod_price >= 10;

IN操作符：

SELECT vend_id, prod_name, prod_price

FROM Products

WHERE vend_id IN ('DLL01', 'BRS01')

ORDER BY prod_name;

NOT操作符：

SELECT vend_id, prod_name, prod_price

FROM Products

WHERE NOT vend_id = 'DLL01'

ORDER BY prod_name;