Common Error Part1

These are errors which i encountered working today..I have put solution for them with details

Error :  Scheduling Error for workflow, workflow [id = X] could not be retrieved from the repository
Reason : Your workflow and related object are not checked in
Solution : Checkin workflow and related objects


Error :  Schedule Workflow: ERROR: Workflow [wf_name]: Workflow not scheduled
Reason :   Your are using resuable scheduler and it is not checked in
Solution :  Checkin resuable scheduler

Error :  Input sources to SQ SQ_TRADE have no relationship....there are data flow validation errors.
Reason : Created Source qualifier by manually dragging item from diffrent source but sql override provide
Solution : Over rid the SQL query in source qualifier