Which format is the best for mysql data export?

Question

The best I mean the smallest file size.

Answer 1

gzipped SQL is probably about the best you're going to get. You could copy the actual data files themselves, but then you run the risk of copying a partially modified table, resulting in a broken copy.

mysqldump -h host -u username --password=foo dbname > file.sql

gzip file.sql

Answer 2

mysqldump -h host -u username --password=foo dbname | gzip -9 > file.sql.gz