My client had deleted all customer accidentally. And unfortunate we don't have any backup.
Any way to recover a customer and their history order?
If you're using an external hosting provider, contact them - they might have automated backups set-up of their complete server or just the databases. So you might be able to recover the lost data.
Other than backups, there is no way to recover lost data in such cases.
sales_flat_order
table saves customer email. So Can I manually create customer from email id and can I link those customer again to sales_flat_order table
?