ABAP Programs: Updating multiple entries in a database table

REPORT ZSOURCE1304.
* Work area
TABLES CUSTOMERS.
* Internal table for changed entries
DATA CHANGED_CUSTOMERS LIKE CUSTOMERS OCCURS 50
WITH HEADER LINE.

* Filling the internal table
SELECT * FROM CUSTOMERS INTO TABLE CHANGED_CUSTOMERS
WHERE CITY = SPACE.
LOOP AT CHANGED_CUSTOMERS.
CHANGED_CUSTOMERS-CITY = ‘City unknown’.
MODIFY CHANGED_CUSTOMERS.
ENDLOOP.
* Updating the database table with values from the internal table
UPDATE CUSTOMERS FROM TABLE CHANGED_CUSTOMERS.
* Updating the database table according to a where condition
UPDATE CUSTOMERS SET CITY = ‘City unknown’
WHERE CITY = SPACE.