| # Task: 015 |
|
|
| **Database:** retails |
|
|
| ## Question |
| For each industry, show the number of customers that bought part 309 from China. |
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|
| ## Gold Query |
|
|
| ```sql |
| WITH industries AS ( |
| SELECT DISTINCT c.c_mktsegment AS industry FROM customer c |
| ), |
| china_customers AS ( |
| SELECT |
| c.c_mktsegment AS industry, |
| COUNT(DISTINCT c.c_custkey) AS customer_count |
| FROM customer c |
| JOIN orders o ON c.c_custkey = o.o_custkey |
| JOIN lineitem l ON o.o_orderkey = l.l_orderkey |
| JOIN partsupp ps ON l.l_partkey = ps.ps_partkey AND l.l_suppkey = ps.ps_suppkey |
| JOIN supplier s ON ps.ps_suppkey = s.s_suppkey |
| JOIN nation n ON s.s_nationkey = n.n_nationkey |
| WHERE l.l_partkey = 309 |
| AND n.n_name = 'CHINA' |
| GROUP BY c.c_mktsegment |
| ORDER BY c.c_mktsegment |
| ) |
| SELECT |
| i.industry, |
| COALESCE(cc.customer_count, 0) AS customer_count |
| FROM industries i |
| LEFT JOIN china_customers cc ON i.industry = cc.industry |
| ORDER BY i.industry; |
| ``` |
|
|
| **Execution Result:** |
|
|
| | industry | customer_count | |
| |------------|------------------| |
| | AUTOMOBILE | 0 | |
| | BUILDING | 0 | |
| | FURNITURE | 0 | |
| | HOUSEHOLD | 0 | |
| | MACHINERY | 0 | |
| |
| *5 rows* |
