This tutorial applies to:Business Intelligence Server Enterprise Edition – Version: 10.1.3.4.0  – Release: 10g
The question was rather frequent – “How to create a table view with two levels of headers?”
i.e. the high-level heading as the table title heading and then another level of heading where there is one sub-heading/title for one set of columns and a different sub-heading for another set of columns
The high-level heading can be created by adding a title view for this.
And then for 2nd level of sub-heading that should be different for one set of columns and another sub-heading for another set of columns, you can achieve this by displaying the table headings as well in addition to the column headings and then set the custom table heading appropriately for the respective set of columns that require the same heading.
To do this, you need to follow a 2-step approach
1) go to the table view and edit the table view properties. Set the ‘display column & table headings’ property to ‘as separate rows’ instead of ‘only column headings’.
2) Then go to each column and set the custom table heading. Set the same table heading for all the columns that require the same heading.