找出从来没有下过单的客户。
- 一个客户只要在订单表里出现过（任何状态的订单都算），就不算“从未下单”。
- 订单表的
customer_id可能为 null，null 不等于任何客户。
输入
customers(customer_id, name, email, city, signup_date, tier)orders(order_id, customer_id, order_ts, status, channel)
输出
列为 customer_id, name，行顺序不限。
从未下单的客户
输入表 （case base，共 2 个 case：base、small）
customers shop/customers
| # | customer_idint64 | namestring | emailstring | citystring | signup_datedate | tierstring |
|---|---|---|---|---|---|---|
| 1 | 1 | Fang Wang | fang.wang@shop.io | Beijing | 2025-03-13 | silver |
| 2 | 2 | Dana Xu | dana.xu@mail.cn | null | 2025-02-17 | silver |
| 3 | 3 | Li Zhou | li.zhou@example.com | Guangzhou | 2025-10-07 | bronze |
| 4 | 4 | Ping Wang | ping.wang@example.com | null | 2025-05-23 | gold |
| 5 | 5 | Tom Zhang | tom.zhang@example.com | Shenzhen | 2025-06-26 | gold |
| 6 | 6 | 王芳 | user06@shop.io | Hangzhou | 2025-02-10 | gold |
| 7 | 7 | Victor Xu | victor.xu@example.com | Shanghai | 2025-12-05 | bronze |
| 8 | 8 | Dana Chen | dana.chen@example.com | Hangzhou | 2025-11-22 | bronze |
| 9 | 9 | Uma Chen | uma.chen@shop.io | Guangzhou | 2025-11-28 | null |
| 10 | 10 | Ivy Zhou | ivy.zhou@shop.io | Hangzhou | 2025-07-14 | gold |
| 11 | 11 | Mia Smith | mia.smith@mail.cn | Shanghai | 2025-04-28 | gold |
| 12 | 12 | Xin Yang | xin.yang@example.com | Chengdu | 2026-01-03 | silver |
| 13 | 13 | Xin Smith | xin.smith@mail.cn | Beijing | 2025-05-07 | silver |
| 14 | 14 | Zoe Xu | zoe.xu@mail.cn | Beijing | 2025-09-18 | silver |
| 15 | 15 | Fang Liu | fang.liu@shop.io | Guangzhou | 2025-08-05 | bronze |
| 16 | 16 | 杨磊 | user16@mail.cn | Shanghai | 2025-12-15 | silver |
| 17 | 17 | Ping Smith | ping.smith@mail.cn | null | 2025-08-11 | bronze |
| 18 | 18 | Oscar Zhou | oscar.zhou@example.com | Shanghai | 2025-11-17 | null |
| 19 | 19 | Kevin Liu | kevin.liu@mail.cn | Chengdu | 2026-02-03 | gold |
| 20 | 20 | Sara Wu | sara.wu@example.com | null | 2025-07-05 | gold |
显示前 20 行，共 50 行
orders shop/orders
| # | order_idint64 | customer_idint64 | order_tsdatetime | statusstring | channelstring |
|---|---|---|---|---|---|
| 1 | 1001 | 39 | 2026-01-01 19:38:00 | paid | app |
| 2 | 1002 | 16 | 2026-01-17 14:07:00 | paid | app |
| 3 | 1003 | 4 | 2026-01-08 15:40:20 | cancelled | web |
| 4 | 1004 | 2 | 2026-05-23 10:48:58 | paid | null |
| 5 | 1005 | 12 | 2026-06-22 11:07:22 | paid | store |
| 6 | 1006 | 17 | 2026-08-15 05:15:25 | paid | web |
| 7 | 1007 | 9 | 2026-06-11 01:00:32 | refunded | store |
| 8 | 1008 | 45 | 2026-09-19 20:47:10 | paid | web |
| 9 | 1009 | 2 | 2025-10-05 04:53:38 | paid | app |
| 10 | 1010 | 4 | 2026-02-19 01:39:54 | paid | app |
| 11 | 1011 | 28 | 2026-03-05 03:04:45 | refunded | store |
| 12 | 1012 | 2 | 2026-08-01 07:09:17 | paid | web |
| 13 | 1013 | 26 | 2026-01-22 03:48:14 | refunded | store |
| 14 | 1014 | 2 | 2026-02-09 01:41:41 | paid | app |
| 15 | 1015 | 5 | 2026-08-03 19:49:04 | refunded | web |
| 16 | 1016 | 26 | 2026-02-16 00:43:43 | refunded | app |
| 17 | 1017 | 9 | 2025-12-06 04:48:57 | pending | app |
| 18 | 1018 | 999 | 2026-05-19 12:13:43 | paid | store |
| 19 | 1019 | 26 | 2026-02-05 15:02:26 | paid | store |
| 20 | 1020 | 44 | 2025-11-24 11:19:00 | cancelled | web |
显示前 20 行，共 200 行
期望输出 （case base，行顺序不限）
| # | customer_idInt64 | nameString |
|---|---|---|
| 1 | 7 | Victor Xu |
| 2 | 15 | Fang Liu |
| 3 | 23 | 李娜 |
| 4 | 33 | Bob Liu |
| 5 | 41 | Lin Zhou |
| 6 | 48 | Hao Zhao |
共 6 行