You can change the query defined in the query specification by using the CHANGE QUERY clause reserved word of the ALTER VIEW statement.
ALTER [ VIEW | VCLASS ] view_name
CHANGE QUERY [ integer ] select_statement [ ; ]
--adding select_statement which query number is 2 and 3 for each
ALTER VIEW b_view ADD QUERY SELECT * FROM a_tbl WHERE id IN (1,2);
ALTER VIEW b_view ADD QUERY SELECT * FROM a_tbl WHERE id = 3;
SELECT * FROM b_view;
id phone
===================================
1 '111-1111'
2 '222-2222'
3 '333-3333'
4 NULL
5 NULL
1 '111-1111'
2 '222-2222'
3 '333-3333'
--altering view changing query number 2
ALTER VIEW b_view CHANGE QUERY 2 SELECT * FROM a_tbl WHERE phone IS NULL;
SELECT * FROM b_view;
id phone
===================================
1 '111-1111'
2 '222-2222'
3 '333-3333'
4 NULL
5 NULL
4 NULL
5 NULL
3 '333-3333'