NewSQLStore we can use SQLStore here because we implement the Store interface, and it used as receiver in execTx and TransferTx methods.

SQLStore struct: This is a concrete implementation of the Store interface, and it wraps around the SQL database (sql.DB).

Store Interface: This defines the contract for the store, which includes all the methods of the Querier (e.g., basic CRUD operations) and a TransferTx method for handling transactions.