Working with dates in ruby and rails on windows, I'm having problems with pre-epoch dates (before 1970) throwing out of range exceptions. I tried using both
DateTime objects, but still have the same problems.
Ruby / Rails pre-epoch dates on windows
I haven't used Oracle's table clusters myself, but I understand that its index table clusters are very much like MS SQL Server's clustered indexes. That is, the row data is physically organized by the clustered index's key.
That makes one ideal for a heavily-accessed column that has a reasonably small number of possible values (compared to the total number of rows), where most queries want to retrieve all rows with a particular value. Because all such rows are physically stored together, disk I/O, particularly seek time, is reduced.
"Reasonably small" is not easily defined, but postal or zip codes in an address table seems reasonable if you're often querying for all addresses in a single code's region. Province/state/territory codes are likely too small a selection for a country-wide address table.
So, you don't want to use them on columns with few possible values (e.g., M/F for gender) because then the clustering doesn't buy you anything and likely costs you for insertions. You also never want to use clustering on "autonumber" surrogate key columns (from sequences in Oracle) because that will create a "hot spot" in the last extent of the table as all insertions must physically happen there. You also don't want to apply clustering to a column value that will be updated because the RDBMS will have to physically move the record to maintain the clustered ordering.