Postgresql 带select的Postgres函数

我想显示以下功能：

select LoanId, BookId ,(OutDate-InDate)*0.3 as money, OutDate-InDate days 
from loans
where (OutDate-InDate)> 30 and OutDate::varchar(4)='2000';

作为输入只有一年，作为输出应该返回select。 我尝试了make函数，但它不起作用。

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有什么想法吗？

我有一张像下面这样的桌子

create table loan(loanid int,bookid int,outdate date,indate date);

还有一些像这样的数据

insert into loan values(1,2,'01-12-2015','01-10-2015'),(1,2,'01-01-2016','08-01-2016');

我使用下面的select查询

select loanid,bookid,(outdate-indate)*0.3 as "money",outdate-indate as "days"
from loan
where (OutDate-InDate)> 30 and extract(year from outdate)='2015'

loanid bookid money days 
------ ------ ----- ---- 
1      2      18.3  61  

现在我有一个函数来做这个工作

create or replace function FN_LOAN_DET(in_year  text)
returns table (loanid int,bookid int,money numeric,days int)
as
$$
select loanid,bookid,(outdate-indate)*0.3 as "money",outdate-indate as "days"
from loan
where (OutDate-InDate)> 30 and  extract(year from outdate)=$1
$$
language sql

当我调用

select*from FN\u LOAN\u DET（'2015'）

loanid bookid money days 
------ ------ ----- ---- 
1      2      18.3  61   

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请分享您的代码，并准确解释哪些代码不起作用。请阅读以下内容，并在问题中添加更多信息，以便我们提供帮助！我试着读懂你的心思以便回答你的问题。。。。但它不起作用。有什么想法吗？