如何使用正在进行的prodataset为5个表实现联接？

Question

我有5个表，它们与父子关系有关。与table1 ->表2->table3->table4->->5一样，这里的箭头显示父到子关系。如何使用正在进行的prodataset从这些相关表中获取记录？如何定义此场景的查询？

Answer 1

下面是一个连接了1个表的示例，只需使用第一种格式将更多的表添加到cQuery。

    ASSIGN
      cQuery = "FOR EACH table1 NO-LOCK ":U
             + "   WHERE table1.product_obj = ":U + QUOTER(cProduct)
             + "     AND table1.role_obj    = ":U + QUOTER(cRole)
             + "  ,FIRST table2 NO-LOCK ":U
             + "   WHERE table2.criterion_obj = table1.criterion_obj":U.

    hQuery:SET-BUFFERS(BUFFER table1:HANDLE, BUFFER table2:HANDLE).

    hQuery:QUERY-PREPARE(cQuery) NO-ERROR.
    hQuery:QUERY-OPEN() NO-ERROR.
    hQuery:GET-FIRST() NO-ERROR.

    DO  WHILE NOT hQuery:QUERY-OFF-END:
        <put logic here>
        hQuery:GET-NEXT() NO-ERROR.
    END.

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对于ProDataSets，需要定义临时表，然后创建ProDataSets

手册中的示例：

DEFINE TEMP-TABLE ttOrder LIKE Order
    FIELD OrderTotal AS DECIMAL
    FIELD CustName LIKE Customer.NAME
    FIELD RepName LIKE SalesRep.RepName.

DEFINE TEMP-TABLE ttOline LIKE OrderLine.

DEFINE TEMP-TABLE ttItem
    FIELD ItemNum LIKE ITEM.ItemNum
    FIELD ItemName LIKE ITEM.ItemName
    FIELD Price LIKE ITEM.Price
    FIELD Weight LIKE ITEM.Weight
    FIELD OnHand LIKE ITEM.OnHand
    FIELD OnOrder LIKE ITEM.OnOrder.

DEFINE DATASET dsOrder FOR ttOrder, ttOline, ttItem
DATA-RELATION OrderLine FOR ttOrder, ttOline
RELATION-FIELDS (OrderNum, OrderNum)
DATA-RELATION LineItem FOR ttOline, ttItem
RELATION-FIELDS (ItemNum, ItemNum).

DEFINE VARIABLE hDSOrder AS HANDLE NO-UNDO.
hDSOrder = DATASET dsOrder:HANDLE.

DEFINE QUERY qOrder FOR Order, Customer, SalesRep.
DEFINE QUERY qItem FOR ITEM.
DEFINE DATA-SOURCE srcOrder FOR QUERY qOrder
Order KEYS (OrderNum), Customer KEYS (CustNum), SalesRep KEYS (SalesRep).
DEFINE DATA-SOURCE srcOline FOR OrderLine.
DEFINE DATA-SOURCE srcItem FOR QUERY qItem ITEM KEYS (ItemNum).

BUFFER ttOrder:ATTACH-DATA-SOURCE(DATA-SOURCE srcOrder:HANDLE,
"Customer.Name,CustName").
BUFFER ttOline:ATTACH-DATA-SOURCE(DATA-SOURCE srcOline:HANDLE).
BUFFER ttItem:ATTACH-DATA-SOURCE(DATA-SOURCE srcItem:HANDLE).

QUERY qOrder:QUERY-PREPARE("FOR EACH Order WHERE Order.OrderNum = 1, " +
    "FIRST Customer OF Order, FIRST SalesRep OF Order"). /* setup query to fill 
     dataset */

hDSOrder:FILL(). /* fill the ProDataSet as a whole */