将数据从一个SQLite数据库复制到另一个数据库

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INSERT INTO X.TABLE SELECT * FROM Y.TABLE;

INSERT INTO X.TABLE(fieldname1, fieldname2) SELECT fieldname1, fieldname2 FROM Y.TABLE;

-(void) createCopyDatabase{
          NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
          NSString *documentsDir = [paths objectAtIndex:0];
          NSString *maindbPath = [documentsDir stringByAppendingPathComponent:@"User.sqlite"];;
          NSString *newdbPath = [documentsDir stringByAppendingPathComponent:@"User_copy.sqlite"];
          NSFileManager *fileManager = [NSFileManager defaultManager];
          char *error;
         if ([fileManager fileExistsAtPath:newdbPath]) {
             [fileManager removeItemAtPath:newdbPath error:nil];
         sqlite3 *database;
         //open database
        if (sqlite3_open([newdbPath UTF8String], &database)!=SQLITE_OK) {
            NSLog(@"Error to open database");
        NSString *attachQuery = [NSString stringWithFormat:@"ATTACH DATABASE \"%@\" AS aDB",maindbPath];
       sqlite3_exec(database, [attachQuery UTF8String], NULL, NULL, &error);
       if (error) {
           NSLog(@"Error to Attach = %s",error);
       //Query for copy Table
       NSString *sqlString = @"CREATE TABLE Info AS SELECT * FROM aDB.Info";
       sqlite3_exec(database, [sqlString UTF8String], NULL, NULL, &error);
        if (error) {
            NSLog(@"Error to copy database = %s",error);
        //Query for copy Table with Where Clause
        sqlString = @"CREATE TABLE comments AS SELECT * FROM aDB.comments Where user_name = 'XYZ'";
        sqlite3_exec(database, [sqlString UTF8String], NULL, NULL, &error);
        if (error) {
            NSLog(@"Error to copy database = %s",error);

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