What are the performance implications of storing some data across 2 databases instead of duplicating this data in both databases? ie. is example 1 significantly slower than example 2:
SELECT Users.User.*, Transactions.Sales.date
FROM Users.User, Transactions.Sales
SELECT Users.User.*, Users.Sales.date
FROM Users.User, Users.Sales
Note in Example 2 the database Users would be significantly larger as it has data duplicated from the database Transactions.
Thanks for any help.