How to delete all scheduler jobs at a time?

How to delete all scheduler jobs at a time?

Use this code in Anonymous window 

for(CronTrigger cron :[select id from CronTrigger ])

{

  System.abortJob(cron.id);

}

After executing above code please check the  scheduled job.

How to check that?

setup-->jobs-->scheduled job 

Now question is whats cron trigger?

CornTrigger is an object in salesforce which contains schedule information for a scheduled job. It contains the CronExpression,NextFireTime,LastFireTime,status etc .

SELECT ID, CronExpression, CronJobDetail.Name, CronJobDetailId, EndTime, NextFireTime, PreviousFireTime, StartTime, State, TimesTriggered FROM CronTrigger

For Information refer below link:

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_scheduler.htm