i have some problems with upgrading from 1.9.1.8 to 1.9.6.1

few sql queries from "install/mssql/constraints.sql" cant be executed:

The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_yaf_PollVote_yaf_Poll". The conflict occurred in database "MyDbName", table "dbo.yaf_Poll", column 'PollID'.

+ few more

my question is: if i upgrade successfuly everything except "constraints.sql" what will happen? can forum run this way normaly?