Hi,
You can create filter in BW BEx query by using BEx Query Designer.
In Query Designer, you will find two area displayed for filter selection. One is Characteristic Restrictions area to the left which is the fixed filter pane and second is the Default Values area to the right which is the dynamic filter pane.
Please refer the following link regarding how to define filter in BEx Query Designer:
http://help.sap.com/saphelp_sm71_sp08/helpdata/en/42/fcf20384631a71e10000000a422035/content.htm
Please refer the following link regarding working with filters:
http://help.sap.com/saphelp_sm71_sp08/helpdata/en/46/027ef96fd33d54e10000000a155369/frameset.htmHi,
Thanks & Regards,
Sapna