Purpose
ROWNUM is a pseudo column that is assigned an incremental unique integer value for records of a table or subselects, beginning with 1. 
Usage Notes
Exasol implements ROWNUM adhering to the overall SQL semantics. 
- ROWNUMcannot be combined with other conditions in the- WHEREclause. Anything you put into the- WHEREclause of a statement filters input data. To avoid confusion and seemingly wrong results, we only allow- ROWNUMin situations where the result is in line with Oracle's semantic.
- ROWNUMcannot be used in combination with the PRIMARY KEY, UNIQUE, and FOREIGN KEY statements.
Example
SELECT SALES_ID, ROWNUM 
FROM SALES 
WHERE ROWNUM <10;| SALES_ID | ROWNUM | 
| 389577429 | 1 | 
| 321740964 | 2 | 
| 389577438 | 3 | 
| 253762032 | 4 | 
| 321740973 | 5 | 
| 389577447 | 6 | 
| 458941123 | 7 | 
| 389577513 | 8 | 
| 389577522 | 9 |