Some customers have run into an error when installing the 4.5 update that indicates there is a duplicate column named fPinned on the HS_Request_History table. This error can be fixed by following the steps below.
Select * from HS_Migrations;
INSERT INTO `HS_Migrations` (`migration`, `batch`) VALUES ('2016_02_18_211111_add_pinned_to_request_history', 2);Edit the batch value to reflect the value that you noted above. After running this insert query you can return to the installer page and continue with the installation.