使用数据处理函数

select vend_name ,upper(vend_name) as vend_name_upcase from vendors order by vend_name;

upper函数是将字符全部大写

select vend_name ,lower(vend_name) as vend_name_upcase from vendors order by vend_name;

lower()函数是将字符全部小写

select cust_name,cust_contact from customers where soundex(cust_contact) = soundex('y lie');

soundex()函数是找出和所给字符串读音很像的匹配行，注意  sql语句格式

b

select cust_id,order_num from orders where order_date = '2005-09-01';

这个语句并不安全，如果order_num中包含时间，这个语句搜索失败

select cust_id,order_num from orders where date(order_date) between '2005-09-01' and '2005-09-30';

date()函数只提取日期，多余的不管，如果想筛选出2005年9月份所有订单用接下来的语句

select cust_id,order_num from orders where year(order_date) =2005 and month(order_date)=9;

year()函数和month()函数与date()函数作用相同，仅提取对应时期