Indsæt række hvis værdi i kolonnen med primary key ikke eksistere

SET TRANSACTION ISOLATION LEVEL { SERIALIZABLE }
START TRANSACTION
IF NOT EXISTS SELECT 1 FROM galleries WHERE GalleriGuid = @GalleriGuid
BEGIN
INSERT INTO galleries (GalleriGuid, GalleriName, GalleriUploader, GalleriCreateDate) VALUES (@GalleriGuid, @GalleriName, @GalleriUploader, @GalleriCreateDate)
COMMIT
END
ELSE
ROLLBACK

OleDbConnection conn = new OleDbConnection(WebConfigurationManager.ConnectionStrings["ImageService"].ConnectionString);

        using (conn)
        {
            conn.Open();

            OleDbCommand cmd = conn.CreateCommand();
            OleDbTransaction myTrans;

            // Start a local transaction
            myTrans = conn.BeginTransaction(IsolationLevel.Serializable);
            // Assign transaction object for a pending local transaction
            cmd.Connection = conn;
            cmd.Transaction = myTrans;

            string sql = "";
            sql += "IF NOT EXISTS SELECT 1 FROM galleries WHERE GalleriGuid = @GalleriGuid ";
            sql += "BEGIN";
            sql += " " + "INSERT INTO galleries (GalleriGuid, GalleriName, GalleriUploader, GalleriCreateDate) VALUES (@GalleriGuid, @GalleriName, @GalleriUploader, @GalleriCreateDate)";
            sql += "END ";
            sql += "INSERT INTO images(ImgGuid, ImgPath, ImgOriginalFileName, GalleriGuid, ImgUploadDate) VALUES (@ImgGuid, @ImgPath, @ImgOriginalFileName, @GalleriGuid, @ImgUploadDate)";

            cmd.CommandText = sql;

            cmd.Parameters.AddWithValue("@GalleriGuid", galleriGuid);
            cmd.Parameters.AddWithValue("@GalleriName", galleriName);
            cmd.Parameters.AddWithValue("@GalleriUploader", galleriUploader);
            cmd.Parameters.AddWithValue("@GalleriCreateDate", uploadDate);
            cmd.Parameters.AddWithValue("@ImgGuid", imageGuid);
            cmd.Parameters.AddWithValue("@ImgPath", path);
            cmd.Parameters.AddWithValue("@ImgOriginalFileName", originalFilename);
            cmd.Parameters.AddWithValue("@ImgUploadDate", uploadDate);

            cmd.ExecuteNonQuery();

            myTrans.Commit();
        }