--Main database
CREATE TABLE [t_test](
    [f_id] INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
    [f_some_data] VARCHAR2(50), 
    [f_timestamp] datetime NOT NULL DEFAULT (datetime('now')));

--BackUp database
CREATE TABLE [t_test](
    [f_id] INTEGER, 
    [f_some_data] VARCHAR2(50), 
    [f_timestamp] datetime;

@echo off

for %%F in (BackUp.db)  do set BackUpFileTime=%%~tF
echo %BackUpFileTime%

sqlite3 MainDB.db "ATTACH DATABASE 'BackUp.db' as 'backup';insert into backup.t_test select * from main.t_test where f_timestamp > datetime('%BackUpFileTime%');"

@echo off

for %%F in (BackUp.db)  do set BackUpFileTime=%%~tF
echo %BackUpFileTime%

if not exist "BackUp.db"{
  type NUL  > BackUp.db
} 
sqlite3 MainDB.db "ATTACH DATABASE 'BackUp.db' as 'backup';insert into backup.t_test select * from main.t_test where f_timestamp > datetime('%BackUpFileTime%');"

f_timestamp