Having problem with Timestamp

Scenario: Two tables (table1, table2) with this开发者_如何学JAVA format: id:short; timestamp:short; price:single

The data in both table are thesame except the timestamp. Timestamp is given as a unix_time in ms.

Question: What is minimum time difference between the timestamps of same record in table1 and table2.

In theory, the minimum time difference would be 0 or even 1ms. In practice wouldn't the time difference be a function of what it takes to put the data into the table along with other external performance factors?

One question I would have about the tables is why is the same record being stored in two places?