mysql语句之计算字段和数据处理函数

1.SELECT Concat(vend_name,' (',vend_country, ')') FROM table_name
ORDER BY vend_name;

Concat()拼接串，它把多个串连接起来形成一个较长的串，其中有多个或一个指定的串，每个串中间用逗号分隔。

2.SELECT Concat(RTrim(vend_name),' (',RTrim(vend_country), ')') FROM table_name
ORDER BY vend_name;

RTrim()函数去掉值右边的所有空格。同理LTrim()去掉值左边的所有空格。

3.SELECT Concat(RTrim(vend_name),' (',RTrim(vend_country), ')') AS vend_title
FROM table_name ORDER BY vend_name;

设输出的列名为vend_title

4.SELECT prod_id,
quantity,
item_price,
quantity*item_price AS expanded_price
FROM orderitems
WHERE order_num=2005;

expanded_price作为新列在后面输出。内容为前两列的乘积。

5.SELECT vend_name,Upper(vend_name) AS vend_name_upcase
FROM table_name
ORDER BY vend_name;

Upper()函数将文本转换成大写。

6.SELECT cust_id,order_num FROM table_name WHERE Date(order_date) 
BETWEEN '2005-09-01' AND '2005-909-30';

返回日期在范围内的所有信息。