[#5341] - Linechart with Y: Double and X:String displays only one value /category

Hello,

I have a line chart, that displays Y: Double values X: String values .
The selection is
select charge, avg(ic_ist_tc) as ic,
0 as ic_charge,messdatum from tbl_physikal_eigensch
where $X{NOTIN,charge, Chargennr} and matnr = $P{Materialnr} and $X{IN,cast(feld as text),Feldstaerke} and
messdatum > CURRENT_DATE - $P!{Zeitraum} group by ic_ist_tc, charge, messdatum
union select charge,avg(ic_ist_tc) ,avg(ic_ist_tc )
as ic_charge, messdatum from tbl_physikal_eigensch
where $X{IN ,charge, Chargennr} and matnr = $P{Materialnr} and $X{IN,cast(feld as text),Feldstaerke} and
messdatum > CURRENT_DATE - $P!{Zeitraum} group by ic_ist_tc, charge, messdatum

and the variables are:
charge java.lang.string
ic_charge java.lang.Double

My problem is, that the chart displays only 1 value whilst there are 3 values in the selection :

Charge ic_charge

44442 1421.039815 1421.039815 7/16/15 6:56 AM

44442 1765.839207 1765.839207 7/16/15 6:59 AM

44442 2083.45303 2083.45303 7/16/15 7:03 AM
and in the attached chart there is only the value 2083 displayed.

Please give me a hint, how I get 3 values for one category displayed.

Another question: It is possible to overlap 2 charts or 2 series of one chart?
I'd like to draw the points of one value (series) and then the points of the second value(series).

Thanks and regards

Rainer