拼接:将值联结到一起构成单个值
MySQL使用Concat()函数来实现拼接
SELECT Concat(vend_name, '(', vend_country, ')')
FROM vendors
ORDER BY vend_name;
删除数据多余空格
RTrim/LTrim/Trim(xxx)
使用别名
别名是一个字段或值的替换名
AS xxx
SELECT Concat(vend_name, '(', vend_country, ')') AS vend_title// 任何客户机应用可按名引用这个列
FROM vendors
ORDER BY vend_name;
执行算术运算
SELECT prod_id,
quantity,
item_price,
quantity*item_price AS expanded_price
FROM orderitems
WHERE order_num = 2005;
支持的基本算术操作符
+
-
*
/