Manage parent/child table
-- Employee (aka operator) EMP exists.
--
employee {EMP}
      PK {EMP}


-- Customer CST exists.
--
customer {CST}
      PK {CST}


-- On date RFQ_DTE, request for quotation
-- number RFQ_NO was received from customer CST.
--
rfq_in {CST, RFQ_NO, RFQ_DTE}
    PK {CST, RFQ_NO}

FK {CST} REFERENCES customer {CST}


-- Project PRO was started on date PRO_DTE
-- in response to request for quotation
-- number RFQ_NO from customer CST.
--
project {PRO, CST, RFQ_NO, PRO_DTE}
     PK {PRO}
     AK {CST, RFQ_NO}

FK {CST, RFQ_NO} REFERENCES rfq_in {CST, RFQ_NO}


-- Offer revision REV for project PRO
-- was created on date OFR_DTE.
--
offer {PRO, REV, OFR_DTE}
   PK {PRO, REV}

FK1 {PRO} REFERENCES project {PRO}


-- On date OW_DTE employee EMP spent OW_HRS hours
-- working on offer revision REV for project PRO.
--
offer_work {PRO, REV, EMP, OW_DTE, OW_HRS}
        PK {PRO, REV, EMP, OW_DTE}

FK1 {PRO, REV} REFERENCES offer {PRO, REV}

FK2 {EMP} REFERENCES employee {EMP}


-- Offer revision REV for project PRO
-- was accepted and approved on date APR_DTE.
--
accepted {PRO, REV, APR_DTE}
      PK {PRO}

FK {PRO, REV} REFERENCES offer {PRO, REV}


-- On date PW_DTE employee EMP spent PW_HRS hours
-- working on project PRO.
--
project_work {PRO, EMP, PW_DTE, PW_HRS}
          PK {PRO, EMP, PW_DTE}

FK1 {PRO} REFERENCES accepted {PRO}
FK2 {EMP} REFERENCES employee {EMP}


Create a view to report work hours.

CREATE VIEW work_hours
AS
SELECT OW_DTE AS DTE
     , EMP
     , OW_HRS AS HRS
     , PRO
     , 'O'    AS WRK_TYPE
     , ('offer revision ' || REV) AS DETAIL
FROM offer_work
UNION
SELECT PW_DTE AS DTE
     , EMP
     , PW_HRS AS HRS
     , PRO
     , 'P'    AS WRK_TYPE
     , 'some project work' AS DETAIL
FROM project_work
;


Note:

All attributes (columns) NOT NULL

PK = Primary Key
AK = Alternate Key (Unique)
FK = Foreign Key