Postgresql CASE 语句 - 我可以在 SELECT 中使用 CASE 的返回值吗

Postgresql CASE 语句 - 我可以在 SELECT 中使用 CASE 的返回值吗？

sql
SELECT customer_name, 
       CASE WHEN total_purchase > 1000 THEN 'VIP' 
            ELSE 'Regular' 
       END AS customer_type 
FROM customers;

sql
SELECT product_name, 
       CASE WHEN price < 10 THEN 'Cheap' 
            WHEN price >= 10 AND price < 100 THEN 'Affordable' 
            WHEN price >= 100 AND price < 1000 THEN 'Expensive' 
            ELSE 'Very Expensive' 
       END AS price_category 
FROM products;

sql
SELECT order_id,
       CASE WHEN order_status = 'pending' AND payment_status = 'unpaid' THEN 'Waiting for Payment'
            WHEN order_status = 'pending' AND payment_status = 'paid' THEN 'Processing'
            WHEN order_status = 'shipped' THEN 'Shipped'
            WHEN order_status = 'delivered' THEN 'Delivered'
            ELSE 'Unknown'
       END AS order_status_description
FROM orders;

sql
-- 示例1：根据购买金额分类客户类型
SELECT customer_name, 
       CASE WHEN total_purchase > 1000 THEN 'VIP' 
            ELSE 'Regular' 
       END AS customer_type 
FROM customers;
-- 示例2：根据产品价格分类价格区间
SELECT product_name, 
       CASE WHEN price < 10 THEN 'Cheap' 
            WHEN price >= 10 AND price < 100 THEN 'Affordable' 
            WHEN price >= 100 AND price < 1000 THEN 'Expensive' 
            ELSE 'Very Expensive' 
       END AS price_category 
FROM products;
-- 示例3：根据订单状态和付款状态描述订单状态
SELECT order_id,
       CASE WHEN order_status = 'pending' AND payment_status = 'unpaid' THEN 'Waiting for Payment'
            WHEN order_status = 'pending' AND payment_status = 'paid' THEN 'Processing'
            WHEN order_status = 'shipped' THEN 'Shipped'
            WHEN order_status = 'delivered' THEN 'Delivered'
            ELSE 'Unknown'
       END AS order_status_description
FROM orders;