[ABAP] OpenSQL: Coalesce – Fehlende SQL-Werte (NULL) ersetzen

* http://www.cadaxo.com/sql-cockpit/neue-open-sql-features-ab-abap-7-40-sp8/

* DEMO_SQL_EXPR_COALESCE

* Null-Werte (Nicht vorhandene Email-Adressen), die sich aus dem LEFT OUTER JOIN ergeben, werden durch den String '<leer>' ersetzt
CONSTANTS: co_no_email TYPE ad_smtpadr VALUE '<leer>'.

SELECT u~bname,
       u~persnumber,
       u~addrnumber,
       COALESCE( a~smtp_addr, @co_no_email ) AS email
  INTO TABLE @DATA(it_usr)
  FROM usr21 AS u
  LEFT OUTER JOIN adr6 AS a ON a~persnumber = u~persnumber AND a~addrnumber = u~addrnumber.

IF sy-subrc = 0.
  cl_demo_output=>display( it_usr ).
ENDIF.