Hit an issue recently where a csv file was being transformed through an SSIS package but persisting to the database as zero value integers for all null value columns.
Spent time examining table constraints through trying to establish why this was occurring. It’s not the SSIS package because the file preview isn’t showing zeros right? Nope, guess again it is the SSIS package. Take a look at the Flat File flow component and tick the box as follows, job done.