SQL第5课__高级过滤数据

操作符

用来联结或改变WEHERE子句中的子句的关键字，也称为逻辑操作符。

AND操作符（同时满足条件）

一个AND两个条件，如果有多个条件，那么两个条件之间加一个AND

SELECT prod_id,prod_price,prod_name 
FROM products
WHERE vend_id  = 'DLL01' AND prod_price<=4
ORDER BY prod_name

OR操作符（第1个条件满足，不管第二个，满不满足都将被检索出）

SELECT prod_id,prod_price,prod_name 
FROM products
WHERE vend_id  = 'DLL01' OR vend_id  = 'DLL02'

求值顺序

猜猜区别

SELECT vend_id,prod_price,prod_name 
FROM products
WHERE vend_id  = 'DLL01' OR vend_id = 'BRS01' AND prod_price >= 10

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

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

前两个一样，AND的优先级比较高

最后一个

IN操作符

SELECT vend_id,prod_name,prod_price
FROM products
WHERE vend_id IN ('DLL01','BRS01')

NOT操作符

SELECT prod_id,prod_price,prod_name 
FROM products
WHERE prod_id 
NOT BETWEEN 'BR01' AND 'RYL01'