[LeetCode/SQL] 1661. Average Time of Process per Machine

[LeetCode/SQL]

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📌 1661. Average Time of Process per Machine

문제

풀이

- machine_id별 processing_time 출력하기 

=> machine_id별 process_id별 start,end timestamp로 열이 나눠져 있으므로,
내부 JOIN을 통해 최종 출력값 도출 하기 

방법

SELECT a1.machine_id
      ,ROUND(AVG(a2.timestamp-a1.timestamp),3) AS processing_time
FROM Activity AS a1
JOIN Activity AS a2
ON a1.machine_id=a2.machine_id AND a1.process_id=a2.process_id
AND a1.activity_type='start' AND a2.activity_type ='end'
GROUP BY a1.machine_id