sql - ORDER BY 输出列小写

Question

我能够毫无问题地运行这个 Postgres 查询:

select
(select product_types.name from product_types
 where product_types.id = products.product_type_id) AS product_type_name
 from products
order by product_type_name

但是当我尝试按小写字母排序时它不起作用:

select
(select product_types.name from product_types
 where product_types.id = products.product_type_id) AS product_type_name
 from products
order by lower(product_type_name)

我收到这个错误:

ERROR:  column "product_type_name" does not exist
LINE 4: order by lower(product_type_name)
                       ^

********** Error **********

ERROR: column "product_type_name" does not exist
SQL state: 42703
Character: 156

有人可以告诉我一些关于这个的信息吗？

Answer 1

乍一看，您的第一个查询可以这样重写:

select pt.name product_type_name from product_types pt
join products p on pt.id = p.product_type_id
order by pt.name

然后，使用 lower 函数进行排序意味着只需将顺序更改为:

order by lower(pt.name)