how to made union or intersect in crystal report selection forumula ?

[xray]

hi there

a have a Database (shown u in attach ) i need this report plz :

i need the all the companies data ( company_info table ) that made any advertise in our magazine ( mag_adv_info table) .

notes :

the idea of the relation is :

( table visit_info ) is the table of all the visits that made by our sales man and if in one of this visits there is advertiseing then i add record in ( mag_adv_info table) and linked by the ID of the ( visit_info table )

how to solve this report to use " report.selectionformula" to get the unintersect ?

thanks