March 2021
Beginner to intermediate
456 pages
12h 49m
Korean
Content preview from 러닝 SQL: 데이터 생성, 검색, 조작까지 데이터 제대로 주무르기
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283
11
장
조건식
-> count(p.amount) num_payments,
-> sum(p.amount) /
-> CASE WHEN count(p.amount) = 0 THEN 1
-> ELSE count(p.amount)
-> END avg_payment
-> FROM customer c
-> LEFT OUTER JOIN payment p
-> ON c.customer_id = p.customer_id
-> GROUP BY c.first_name, c.last_name;
+------------+------------+-----------------+--------------+-------------+
| first_name | last_name | tot_payment_amt | num_payments | avg_payment |
+------------+------------+-----------------+--------------+-------------+
| MARY | SMITH | 118.68 | 32 | 3.708750 |
| PATRICIA | JOHNSON | 128.73 | 27 | 4.767778 |
| LINDA | WILLIAMS | 135.74 | 26 | 5.220769 |
| BARBARA | JONES | 81.78 | ...