4.过滤数据

#where子句过滤数据
SELECT prod_name,prod_price FROM products WHERE prod_price = 3.49;
SELECT prod_name,prod_price FROM products WHERE prod_price > 3.49 ORDER BY prod_price DESC;
#不匹配检查
SELECT vend_id,prod_name FROM products WHERE vend_id != ‘DLL01’;
#范围值
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;