由于列名相同，无法创建视图（并且不能修改列名）

Question

我有以下查询：

SELECT e.fname, e.lname, s.fname, s.lname, e.salary
FROM employee e JOIN
     employee s
     ON s.ssn = e.super_ssn JOIN
     department d 
     ON e.dno = d.dnumber
WHERE d.dname = 'Research'

这对我的意图来说是桃花心的。但是我想创建一个View以便提取对象，而不是每次都必须再次运行查询。问题是，每当我尝试使用CREATE VIEW <name>提交该查询时，都会出现以下错误：column "fname" specified more than once。

我是SQL (Postgres)的新手，只是学习它。

Answer 1

视图中的列必须具有不同的名称。因此，分配新名称，例如：

SELECT e.fname, e.lname,
       s.fname as supervisor_fname, s.lname as supervisor_lname,
       e.salary
FROM employee e JOIN
     employee s
     ON s.ssn = e.super_ssn JOIN
     department d 
     ON e.dno = d.dnumber
WHERE d.dname = 'Research'

Answer 2

您可以使用别名来区分列名称：

CREATE VIEW view_name as
SELECT e.fname e_fname, e.lname e_lname, s.fname s_fname, s.lname s_lname, e.salary
FROM employee e JOIN
     employee s
     ON s.ssn = e.super_ssn JOIN
     department d 
     ON e.dno = d.dnumber
WHERE d.dname = 'Research'