Substract 2列SQL

Question

我有一张表，其中有两列：薪水和新闻报道。我想用工资减去新闻工资并将其存储在新栏目中。我怎么能这样做？

这不起作用：

SELECT employee_id, last_name, salary, round((salary * 0.155 + salary)) AS newsal, SUBSTR(newsal, salary) AS Increase FROM employees;

这也不起作用

SELECT employee_id, last_name, salary, round((salary * 0.155 + salary)) AS newsal, sum(newsal - salary) AS Increase FROM employees;

Answer 1

你不能在别名中使用别名作为列名，你必须重复代码和 只需使用减号

  SELECT employee_id
  , last_name
  , salary
  , round((salary * 0.155 + salary)) AS newsal
  , ( round(salary * 0.155 + salary) -salary) AS Increase 
  FROM employees;

或者你可以使用subselect作为表

select  employee_id
, last_name, salary
, (newsal - salary=  AS Increase
from (
SELECT employee_id
, last_name
, salary
, round((salary * 0.155 + salary)) AS newsal
FROM employees
) t