参考asktom后，随便给一种方法：
SQL> create or replace function long_2_varchar (
2 p_table_owner in all_tab_partitions.table_owner%type,
3 p_table_name in all_tab_partitions.table_name%type,
4 p_partition_name in all_tab_partitions.partition_name%type
5 )
6 return varchar2
7 as
8 l_high_value LONG;
9 begin
10 select high_value
11 into l_high_value
12 from all_tab_partitions
13 where table_owner = p_table_owner
14 and table_name = p_table_name
15 and partition_name = p_partition_name;
16
17 return substr( l_high_value, 1, 4000 );
18 end;
19 /
Function created
SQL> select t.table_name,t.high_value,long_2_varchar(user,t.table_name,t.partition_name) from user_tab_partitions t;
TABLE_NAME HIGH_VALUE LONG_2_VARCHAR(USER,T.TABLE_NA
------------------------------ -------------------------------------------------------------------------------- --------------------------------------------------------------------------------
SALES TO_DATE(' 1999-04-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 1999-04-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 1999-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 1999-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 2000-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 2000-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 1999-10-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 1999-10-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 2000-04-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 2000-04-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 2000-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 2000-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 2000-10-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 2000-10-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
SALES TO_DATE(' 2001-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TO_DATE(' 2001-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
8 rows selected
SQL>