如何将表达式中的结果列重用于另一个结果列 [英] How to reuse a result column in an expression for another result column

问题描述

示例：

SELECT
   (SELECT SUM(...) FROM ...) as turnover,
   (SELECT SUM(...) FROM ...) as cost,
   turnover - cost as profit

确定这是无效的（至少在Postgres中有效），但是如何在查询中实现相同效果而又不重写子查询两次？

Sure this is invalid (at least in Postgres) but how to achieve the same in a query without rewriting the sub-query twice?

推荐答案

像这样：

SELECT
   turnover,
   cost,
   turnover - cost as profit
from (
   (SELECT SUM(...) FROM ...) as turnover,
   (SELECT SUM(...) FROM ...) as cost
   ) as partial_sums

这篇关于如何将表达式中的结果列重用于另一个结果列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！