# CSV vs XLS for import

I need to import data from various database sources. At the moment I plan on importing files via a CSV file or XLS. All the data if in XLS would be on one sheet (notebook). Are there any advantages of using one format over the other? Thanks. David

• It's probably good to know about this. When the importer tries to be too smart, it can work against you. – Szabolcs Nov 14 '14 at 15:37
• Very helpful. That is a gotcha that could take a long time to figure out! – David Kerr Nov 14 '14 at 20:13

Importing CSV files with Import can be much faster and takes less time and memory, although I often resort to reading line by line or as a block using ReadList and do my own conversions when needed.