引用mySQL查询组件

Question

是否有方法在同一查询中引用MySQL查询的部分？

例如：

SELECT 50000 AS starting_principle, .065*50000 AS interest, 
    principle + interest AS principle_plus_interest

查询集中的第三列principle_plus_interest给出了一个错误。除了编写50000 + .065*50000 AS principle_plus_interest之外，还有什么方法可以对此进行编码吗？

Answer 1

您不能引用select列表(或where子句)中的别名。解决这一问题的一种方法是使用子查询：

SELECT starting_principle, 
       interest, 
       principle + interest AS principle_plus_interest 
FROM   (SELECT 50000 AS starting_principle, .065*50000 AS interest
        FROM   some_table) t