Get the source code for Oracle database views and materialized view

Oracle user_views/user_mviews contains source code about the view/materialized views.
SQL> select text from user_views where view_name='V_R_SUM';
TEXT
--------------------------------------------------------------------------------

select to_char(dt_tm, 'YYYY') yy, to_char(DT_TM, 'MM') mm, to_char(DT_TM,'DD') dd, to_char(DT_TM, 'HH24') hh, to_char(DT_TM, 'MI') mi, to_char(DT_TM,'SS') ss, min(price) mi_p, avg(price) a_p, max(price) mx_p from MV_VIX3 group by to_char(dt_tm, 'YYYY'),to_char(DT_TM, 'MM'),to_char(DT_TM,'DD'),to_char(DT_TM, 'HH24'),to_char(DT_TM, 'MI'), to_char(DT_TM,'SS')

SQL> select query from user_mviews where mview_name='MV_ALL_FOR_SUM';
QUERY
--------------------------------------------------------------------------------
select
a.TXN_ROWID,
a.TRN_CUSTOMER_ACCOUNT_NUM,
a.TRN_TRANSACTION_DT daily_txn_dt,
a.TRN_TRANSACTION_AMT,
a.STAR_ROWID,
a.CUSTOMER_ID_NUMBER,
a.STAR_TRAN_DATETIME,
b.TRANSACTION_AMT frd_clm_amt, b.TRANSACTION_DT frd_clm_dt, b.clm_rowid,
c.fee, c.od_rowid
from
tbl_m_txn_star_final a,
tbl_m_txn_star_clm b,
mv_m_txn_star_od c
where a.txn_rowid=b.txn_rowid(+) and
a.txn_rowid=c.txn_rowid(+)

It is very helpful as we can always find out the logic that is used to created the view. This is one of the advantage of using views over tables.