通过拆分列的值来呈现摘要信息

Question

有没有办法用下面的 table 显示以下内容：

customer_id | loan_date  | loan_amount | loan_paid | status
------------+------------+-------------+-----------+--------
customer1     04/02/2010   5000          3850        active
customer2     04/02/2010   3000          3000        completed
customer3     04/02/2010   6500          4300        defaulted
...

平均贷款，所有贷款的标准差，贷款笔数，违约总额，每月收回贷款总额。（我有大约5年的数据）。

我不知道从哪里开始。

Answer 1

这样开始：

SELECT date_trunc('month', loan_date)
     , avg(loan_amount) AS avg_loan
     , stddev_samp(loan_amount)  AS stddev_samp
     , count(*) AS ct_loans
     , count(*) FILTER (WHERE status = 'defaulted') AS ct_defaulted
     , sum(loan_paid) AS sum_paid
FROM   tbl
GROUP  BY 1
ORDER  BY 1;

然后细化。细节不清楚。不确定 loan_paid 的确切含义，以及您想要准确求和的内容。在 "standard deviation" ...

的名称下有多项措施

关于aggregate functions。

关于date_trunc()。

关于GROUP BY 1：

Concatenate multiple result rows of one column into one, group by another column

关于聚合 FILTER 子句：

Aggregate columns with additional (distinct) filters

通过拆分列的值来呈现摘要信息

Presenting summary information with splitting the value of a column

sql

postgresql

aggregate