數據庫設計爲每年支付

Question

目前，我有我的數據庫中的兩個表：

• 「客戶」同列：CUSTOMER_ID，CUSTOMER_NAME
• 「金」與列：payment_id，CUSTOMER_ID，一年，支付 （布爾），付款人

列「年」表示「付款人」支付的年份。

這給了我只有一個支付列：

SELECT customer_id, paid AS paid_for_2017 FROM customers LEFT JOIN payments ON customers.customer_id=payments.customer_id AND year=2017; 

現在我需要一個SELECT查詢，給了我下面的：

customer_name, paid_for_2017, paid_for_2018,... 

我該怎麼辦呢？我應該改變我的數據庫設計嗎？歡迎提出建議。

Answer 1

如果你知道這些年來，你可以使用有條件聚集：

SELECT customer_id, 
     SUM(CASE WHEN year = 2017 THEN paid END) AS paid_for_2017, 
     SUM(CASE WHEN year = 2018 THEN paid END) AS paid_for_2018 
FROM customers c LEFT JOIN 
    payments p 
    ON c.customer_id = p.customer_id 
GROUP BY customer_id;