ROWNUM as a pseudo column equivalent in T-SQL?

Question

When using ROWNUM as a pseudo column how would you write the following query using T-SQL? Here is the full query. I realize it's written in PL/SQL and I will need to change addition objects.

BASE AS (
SELECT NULL AS ES_CMPNY_STATUS_KEY
  ,CSG.CMPNY_STATUS_GROUP
  ,CSG.CMPNY_STATUS_GROUP_ID
  ,CSG.CMPNY_STATUS_REASON
  ,CSG.CMPNY_STATUS_REASON_ID
  ,CSF.CMPNY_CURRENT_STATUS_FLAG
  ,TRUNC(SYSDATE) AS LOAD_DATE
  FROM CMPNY_STATUS_GROUP CSG
  CROSS JOIN CMPNY_CURRENT_STATUS_FLAG CSF
  ORDER BY CSG.CMPNY_STATUS_GROUP, CSG.CMPNY_STATUS_REASON

   )SELECT ROWNUM AS ES_CMPNY_STATUS_KEY
   ,CMPNY_STATUS_GROUP
   ,CMPNY_STATUS_GROUP_ID
   ,CMPNY_STATUS_REASON
   ,CMPNY_STATUS_REASON_ID
   ,CMPNY_CURRENT_STATUS_FLAG
   ,LOAD_DATE
 FROM BASE B
UNION
SELECT 0 AS ES_CMPNY_STATUS_KEY
  ,NULL AS CMPNY_STATUS_GROUP
  ,0 AS CMPNY_STATUS_GROUP_ID
  ,NULL AS CMPNY_STATUS_REASON
  ,0 AS CMPNY_STATUS_REASON_ID
  ,0 AS CMPNY_CURRENT_STATUS_FLAG
  ,TRUNC(SYSDATE) AS LOAD_DATE
  FROM DUAL

Answer 1

Use row_number():

select row_number() over (order by (select null)) as ES_CMPNY_STATUS_KEY

Note that the order by is needed. The (select null) appears -- in practice -- to avoid any additional sorting. In general, though, you would include a column that specifies a sort order for the data you want.