问题
Could anybody tell why oracle allows only one "LONG" datatype column per table.
回答1:
LONGs were stored inline with the table data, so Oracle probably limited it to one per table because of that (performance hit as you'd be scanning over a lot of blocks) whereas LOBs are stored inline for only the first few k then go into the LOB segment for the rest.
As LONGs are totally depreciated and a major pain in the butt to deal with, stay well away from them where possible.
来源：https://stackoverflow.com/questions/13582213/why-oracle-allows-only-one-long-column-per-table