Thanks Marc;
RIODS.REQUEST_CHANGE_HISTORY.CHANGE_DATE is
Data Type : datetime
Length : 8
Numeric Precision : 23
Numeric Scale : 3

In looking at the fact build in cognos data manager, the TIMESTAMP_COL is going through a calculation to derive CHANGE_DATE:
if (DBMS( $Connection )='MICROSOFT SQL SERVER')
then return PosixTime_To_Timestamp( ToInteger( TIMESTAMP_COL ) );
else return ToDate( TIMESTAMP_COL, 'yyyy-mm-dd' );

When i try to test this query in data manager:
SELECT    W."FACT_ID",
    TI."{$TIMESTAMP_COL}",
    W."WI_ID",
    W."PREV_TEAM_AREA_ID",
    W."PREV_CATEGORY_ID",
    W."PREV_ITERATION_ID",
    TP."WI_TYPE",
    W."PREV_OWNER_ID",
    ST."STATE_NAME",
    P."WI_PRIORITY",
    SV."WI_SEVERITY",
    "PREV_COMMENT_COUNT",
    "PREV_SUBSCRIBER_COUNT",
    "PREV_TAGS",
    "PREV_DURATION",
    "PREV_TIME_SPENT",
    "PREV_SUMMARY"
FROM   {$WORKITEM_CHNGS} W
LEFT JOIN {$TIME_TBL} TI ON W."TIME_ID"=TI."TIME_ID"
LEFT JOIN {$TYPE_TBL} TP ON W."PREV_WI_TYPE_ID"=TP."TYPE_ID"
LEFT JOIN {$STATE_TBL} ST ON W."PREV_WI_STATE_ID"=ST."{$STATE_COL}"
LEFT JOIN {$PRIORITY} P ON W."PREV_WI_PRIORITY_ID"=P."PRIORITY_ID"
LEFT JOIN {$SEVERITY} SV ON W."PREV_WI_SEVERITY_ID"=SV."SEVERITY_ID"
 i get prompted for the following variables and i'm not sure of the values to provide:
$TIMESTAMP_COL
$WORKITEM_CHNGS
$TIME_TBL
$TYPE_TBL
$STATE_TBL
$STATE_COL
$PRIORITY
$SEVERITY
and i'm challenged in getting the correct set of values for all...