Need help with SQLite data input

[Larz60+]

You never put anything in the database,
the table was created properly
using the command line interface, here's a snapshot of your database:

Output:
λ sqlite3 example.db
SQLite version 3.21.0 2017-10-24 18:55:49
Enter ".help" for usage hints.
sqlite> .schema
CREATE TABLE customers_main(acctnum TEXT, custname TEXT);
sqlite> select * from customers_main;
sqlite> select count(*) from customers_main;
0
sqlite> .quit