Migration of existing SQL Data
The existing data in .sql format can be imported into Koha by the command,
$ mysql -u root -p koha < sample.sql
where,
sample.sql is the existing data and placed in the root folder
Once the migration is complete,we need to reindex the data so that it appears while searching. First shift to koha user from root user through,
$ su koha
Enter the command,
$ perl -I /usr/share/koha/lib/ /usr/share/koha/bin/migration_tools/rebuild_zebra.pl -r -b -v -a -x
Once reindexing is complete,shift back to root user,
$ su -
For more details refer here