[Stackoverflow] [Progress OpenEdge ABL] PROGRESS 4GL - When to use FOR FIRST, CAN-FIND and FIND FIRST?

[Thiru]

I am new to progress 4GL. I'm always willing to write a proper code and willing to know each end every keyword that we are using but following sample queries giving same results. I don't know when to use FIND FIRST, FOR FIRST and CAN-FIND? Please help me by re-writing with impeccable answer

FOR EACH Customer NO-LOCK:
    FOR FIRST Order OF Customer:
    /*somelogic*/
    END.
END.

FOR EACH Customer NO-LOCK:
    FIND FIRST Order OF Customer NO-LOCK NO-ERROR.
    IF AVAILABLE Order THEN
    /*somelogic*/
END.

FOR EACH Customer NO-LOCK:
  IF CAN-FIND(FIRST  Order OF Customer ) THEN
  DO:
        /*somelogic*/
  END.
END.

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