I have SCN:

```
SELECT TIMESTAMP_TO_SCN(SYSTIMESTAMP) SCN FROM DUAL;

```

I can convert it to time stamp:

```
SELECT SCN_TO_TIMESTAMP(6480157) FROM DUAL;

```

When I want to mix this two select Im getting error:

```
SELECT SCN_TO_TIMESTAMP(SELECT TIMESTAMP_TO_SCN(SYSTIMESTAMP) FROM DUAL) FROM DUAL;

```

`ORA-00936: missing expression`