Use indicator variables when the application requires the database to set a column value to null, such as when executing an INSERT or UPDATE statement.
Indicator variables can be used within a WHERE clause with host variables to indicate a null.
A negative value indicates the value in the associated main variable is to be ignored and PP2 is to send a null to the database for the column.
A zero or positive value specifies the host variable value is to be sent to the database as the column value.
EXEC SQL
INSERT table1 VALUES (:hostvar1 :indvar1)
END-EXEC
EXEC SQL
UPDATE table1
SET col1 = :hostvar1 :indvar1
WHERE col1 = :hostvar2
END-EXEC