mysql - 表名作为列中的值

Question

我有一个练习:

Find names of companies in ascending order. The list should include both supplier names and customer names. There should also be information whether this company is supplier or customer.

它应该看起来像这样:

CompanyName A, Supplier 
CompanytName B, Customer 
CompanyName C, Customer

到目前为止我能做的:

SELECT CompanyName 
FROM suppliers
UNION
SELECT CompanyName
FROM customers
ORDER BY CompanyName ASC;

所以我遗漏了公司是供应商还是客户的信息。欢迎任何帮助，在此先感谢您，对于不好的标题，我们深表歉意。

Answer 1

我认为，根据数据库表的结构，您可能要考虑 JOIN，但如果您需要使用 UNION，我会将以下内容添加到每个表 SELECT 中，如下所示:

SELECT CompanyName, 'Supplier'
FROM suppliers
UNION
SELECT CompanyName, 'Customers'
FROM customers
ORDER BY CompanyName ASC;