It seems to me that in APEX 4.0.2.00.07 (and probably entire 4.0, but can't check at the moment) there's a bug with adding markers to your (bar/column) chart. For a Pie chart it works fine.
If you edit your Chart Attributes you can define a Marker in the Display Settings.
However when you run the page and look at the chart there is no Marker to see.
If you need Markers, there are two workarounds at the moment:
- customise the XML (my preferred option): you set Custom XML in the Chart Attributes to Yes and you change the marker section to the marker you want. You will see marker type="None", but you can easily change that. Below I changed it to Cross, to have a cross marker.
- add another Series in the chart of type Marker, but this is not my preferred option because you lose performance as it will need to run the query twice.When you run the page after you changed the XML, the chart with the marker looks like this (see the cross on top of the bar):
I'm sure the APEX development team will fix it soon, but for now you know a workaround.
