Oracle 18c

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CREATE TABLE EXPORT_TABLE (
  TABLE_OWNER     VARCHAR2(30),
  TABLE_NAME      VARCHAR2(30),
  PARTITION_NAME  VARCHAR2(30),
  HIGH_VALUE      LONG,
  NUM_ROWS        INTEGER
); 
INSERT INTO EXPORT_TABLE
  SELECT 'TO', 'TN', 'PN1', 'TIMESTAMP ''2019-06-26 12:34:56''', 12345 FROM DUAL UNION ALL
  SELECT 'TO', 'TN', 'PN2', 'TIMESTAMP ''2019-06-26 22:22:22''', 54321 FROM DUAL;
2 rows affected

ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
WITH FUNCTION clobToDate( value IN CLOB ) RETURN DATE
  IS
    ts DATE;
  BEGIN
    EXECUTE IMMEDIATE 'BEGIN :ts := ' || value || '; END;' USING OUT ts;
    RETURN ts;
  END;
SELECT table_owner,
       table_name,
       MAX( high_value ) AS max_high_value,
       SUM( num_rows ) AS total_rows
FROM   (
  SELECT TABLE_OWNER,
         TABLE_NAME,
         PARTITION_NAME,
         clobToDate(
           EXTRACTVALUE(
             dbms_xmlgen.getxmltype(
               'SELECT high_value'
               || ' FROM  EXPORT_TABLE'
               || ' WHERE TABLE_OWNER    = ''' || t.table_owner || ''''
               || ' AND   TABLE_NAME     = ''' || t.table_name || ''''
               || ' AND   PARTITION_NAME = ''' || t.partition_name || ''''
             ),
             '//text()'
           )
         ) AS HIGH_VALUE,
         NUM_ROWS
  FROM   EXPORT_TABLE t
)
GROUP BY table_owner, table_name;


TABLE_OWNER
TABLE_NAME
MAX_HIGH_VALUE
TOTAL_ROWS


TO
TN
2019-06-26 22:22:22
66666