如何计算工具保持暂停的平均时间？ oracle sql 开发人员

Question

Im trying to calculate the average time a tool stays on loan. The time a tool stays on loan is the number of days between loan_status_change_date and tool_out_date (table columns). the date type of these 2 columns is ex: 01-SEP-17 whats the best way to approach this?

Answer 1

We can do arithmetic with Oracle dates. It's not clear from the column names which one is the start of the loan and which the end; in the following example I've assumed loan_status_change is when the tool is returned.

select tool
     , avg(loan_status_change - tool_out_date) as avg_loan_days
from   your_table
group by tool
/

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The AVG() function is an aggregate function, so it handles the /ns for us. The substraction is to calculate the length of a particular loan, which is the value you want to average. The result of that substraction already is a number of days, so no further transformation is necessary. If your columns have a time element then the result might not be an integer.