Database question sent to Sean Lahman.

Regarding the Microsoft Access baseball database (catchy name):

Team table has null for HBP and SF before 2000.  Why?  Individual batters have that data.

For instance Mickey Mantle has SF 1954-1968 and null 1951-1953, which is correct.

Isn't team data derived from the data for individual batters and if not how do you verify the team data?