Добавить данные в базу данных с помощью подзапросов

public string InsertContactWithAccount(string contactName, string accountName)
{
    contactName = contactName ?? "Unknown contact";
    accountName = accountName ?? "Unknown account";
    
    var id = Guid.NewGuid();
    var selectQuery = new Select(UserConnection)
            .Column(Column.Parameter(contactName))
            .Column("Id")
        .From("Account")
        .Where("Name").IsEqual(Column.Parameter(accountName)) as Select;
    var insertSelectQuery = new InsertSelect(UserConnection)
        .Into("Contact")
        .Set("Name", "AccountId")
        .FromSelect(selectQuery);

    var affectedRows = insertSelectQuery.Execute();
    var result = $"Inserted new contact with name '{contactName}'" +
                $" and account '{accountName}'." +
                $" Affected {affectedRows} rows.";
    return result;
}

public string InsertAllAccountsContact(string contactName)
{
    contactName = contactName ?? "Unknown contact";

    var id = Guid.NewGuid();
    var insertSelectQuery = new InsertSelect(UserConnection)
        .Into("Contact")
        .Set("Name", "AccountId")
        .FromSelect(
            new Select(UserConnection)
                .Column(Column.Parameter(contactName))
                .Column("Id")
                .From("Account") as Select);

    var affectedRows = insertSelectQuery.Execute();
    var result = $"Inserted {affectedRows} new contacts with name '{contactName}'";
    return result;
}