Validation on FromDate and ToDate

public boolean validateWrite()

{

    boolean ret;

    SS_CategoryTradeAgreement      categoryTradeAgreement;

    ;

    ret = super();

    if(this.ToDate < this.FromDate)

        ret = checkFailed("Todate should be greater than or equal to Fromdate");

    while select categoryTradeAgreement where  categoryTradeAgreement.Category == this.Category

                                            && categoryTradeAgreement.Vendor == this.Vendor

                                            && categoryTradeAgreement.RecId != this.RecId

                                            && (( categoryTradeAgreement.FromDate <= this.FromDate && categoryTradeAgreement.ToDate >= this.FromDate)

                                                       ||(categoryTradeAgreement.FromDate <= this.ToDate   && categoryTradeAgreement.ToDate >= this.ToDate))

    {

    ret = checkfailed(strfmt("Duplicate Entries are not allowed - Same record is there for Vendor - %1 with Category %2 of period %3 - %4" ,

                         categoryTradeAgreement.Vendor,categoryTradeAgreement.Category,categoryTradeAgreement.FromDate,categoryTradeAgreement.ToDate));

    break;

    }

    return ret;

}

Join by Query

static void CustTableSales(Args _args)

{

    Query                             query;

    QueryRun                       queryrun;

    QueryBuildDataSource     qbds1;

    QueryBuildDataSource     qbds2;

    QueryBuildRange             qbr1;

    QueryBuildRange             qbr2;

    CustTable                        custTable;

    ;

    query     = new query();

    qbds1    =   query.addDataSource(tablenum(CustTable));

    qbds1.addSortField(fieldnum(custTable,AccountNum),Sortorder::Descending);

    qbr1    = qbds1.addRange(fieldnum(custTable,custGroup));

    qbr1.value(queryvalue('10'));

    qbr2     =  qbds1.addRange(fieldnum(custTable,Blocked));

    qbr2.value(queryvalue(CustVendorBlocked::No));

    qbds2   = qbds1.addDataSource(tablenum(SalesTable));

    qbds2.relations(false);

    qbds2.joinMode(joinmode::ExistsJoin);

    qbds2.addLink(fieldnum(CustTable,AccountNum),fieldnum(SalesTable,CustAccount));

    queryrun    = new queryrun(query);

    while(queryrun.next())

    {

    custTable   = queryrun.get(tablenum(custTable));

    info(strfmt("%1 - %2",custtable.AccountNum,custTable.Name));

    }

}