Surely not Excel, because SSIS will parse the file and try to determine datatypes.
There's no actual difference between CSV and Notepad, because both are flat files (entirely text).
I think fixed width or ragged right is a bit faster than a delimited flat file, since SSIS doesn't have to look for delimiters. Which means .txt (with no delimiter) can be a bit faster than CSV.
If you have only date, time or integer values in your flat file, you can turn on
FastParse to get even faster speeds.
Long story short, flat files are the fastest.
MCSA SQL Server 2012 - Please mark posts as answered where appropriate.
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