Read/Write to Encrypted file without Decrypting the whole file - possible?

I have an encrypted sqlite database which decrypts when my application starts and encrypts when the app closes down - it is encrypted using the Rijndael method

Currently the data is retrieved by my application when the database is decrypted into a separate file

Is it possible to read/write to the encrypted database without decrypting the whole database into a separate file as once it is decrypted it contains data which my competitors could use?