We will make use of NULL indicator in order to store a NULL value in any column of a DB2 table. Firstly, we should move a value -1 in the NULL indicator in our COBOL-DB2 program. After that we execute UPDATE or INSERT query to store the NULL value.
For example, if we have to update a NULL value in the ORDER_DESCRIPTION column of the ORDER table where ORDER_ID is 3345612.
A020-UPDATE-ORDERS. MOVE -1 TO ORDER-DESCRIPTION-N MOVE SPACES TO ORDER-DESCRIPTION-DATA EXEC SQL UPDATE ORDERS SET ORDER_DESCRIPTION = :ORDER-DESCRIPTION-DATA :ORDER-DESCRIPTION-N WHERE ORDER_ID = ‘3345612’ END-SQL.
ORDER-DESCRIPTION-N is the NULL indicator here. The important point to note here is that the second line in the paragraph i.e the line highlighted with orange is optional. Once we have moved -1 in the null indicator then no matter what value we give in the data field, only NULL value will be stored in DB2 table.