sqlite multi db management

1. open table
2. sqlite.exec ( &sqlite, "attach database 'mydb-log.db' as log );

만약 여러 테이블을 중복없이 각 데이터베이스에 만들었다면, 별도의 데이터베이스이름('log')을 사용하지 않고 바로 query 가 가능하다.

특정 테이블을 메모리 db로 사용하고자 한다면,


sqlite.exec ( &sqlite, "attach database ':memory:' as log );
로 한 후
아래의 코드를 이용하여 로딩한다.
loadOrSaveDb(&sqlite, "log", "mydb-log.db", 0);

memory db를 사용한 경우 별도로 저장을 해 주어야 한다.
저장시는,

loadOrSaveDb(&sqlite, "log", "mydb-log.db", 1);
와 같이 하면 된다.

아래는, sqlite 사이트에서 가져온 코드에 약간 수정한 것임.
(데이터베이스 이름을 선택할 수 있게 수정)


int loadOrSaveDb(sqlite3 *pInMemory, const char* dbname, const char *zFilename, int isSave){
  int rc;                   /* Function return code */
  sqlite3 *pFile;           /* Database connection opened on zFilename */
  sqlite3_backup *pBackup;  /* Backup object used to copy data */
  sqlite3 *pTo;             /* Database to copy to (pFile or pInMemory) */
  sqlite3 *pFrom;           /* Database to copy from (pFile or pInMemory) */
char *pFromDBName, *pToDBName;
  /* Open the database file identified by zFilename. Exit early if this fails
  ** for any reason. */
  rc = sqlite3_open(zFilename, &pFile);
  if( rc==SQLITE_OK ){

    /* If this is a 'load' operation (isSave==0), then data is copied
    ** from the database file just opened to database pInMemory.
    ** Otherwise, if this is a 'save' operation (isSave==1), then data
    ** is copied from pInMemory to pFile.  Set the variables pFrom and
    ** pTo accordingly. */
    pFrom = (isSave ? pInMemory : pFile);
    pTo   = (isSave ? pFile     : pInMemory);
    pFromDBName = (isSave ? dbname : "main");
    pToDBName   = (isSave ? "main"     : dbname);

    /* Set up the backup procedure to copy from the "main" database of
    ** connection pFile to the main database of connection pInMemory.
    ** If something goes wrong, pBackup will be set to NULL and an error
    ** code and  message left in connection pTo.
    **
    ** If the backup object is successfully created, call backup_step()
    ** to copy data from pFile to pInMemory. Then call backup_finish()
    ** to release resources associated with the pBackup object.  If an
    ** error occurred, then  an error code and message will be left in
    ** connection pTo. If no error occurred, then the error code belonging
    ** to pTo is set to SQLITE_OK.
    */
    pBackup = sqlite3_backup_init(pTo, pToDBName, pFrom, pFromDBName);
    if( pBackup ){
      (void)sqlite3_backup_step(pBackup, -1);
      (void)sqlite3_backup_finish(pBackup);
    }
    rc = sqlite3_errcode(pTo);
  }

  /* Close the database connection opened on database file zFilename
  ** and return the result of this function. */
  (void)sqlite3_close(pFile);
  return rc;
}