Convert LONG format to DATE without a function - oracle

Question

The column HIGH_VALUE has data similar to below, of type LONG, and always has the same length:
TIMESTAMP' 2019-01-30 00:00:00'
How can I convert it to a DATE type without using a function?
My overall goal is to create a result set which can then be used as an inner query for other aggregations. For example, I would like to be able to sum the number of rows over a year according to the date produced by converting the HIGH_VALUE column to a date.
I have only read permissions on this database and therefore cannot create functions. I've seen other solutions on StackOverflow and other sites, but they all require creating a function.
ALL_TAB_PARTITIONS is a standard built-in Oracle table and therefore I'm not including the table structure. In case that's an issue, please let me know and I will create an example table.
An example query and the data one row that results from this query follows. Note that I cannot create tables on this database so I will also need an a method that works without creating a temporary table.
Insert into EXPORT_TABLE (TABLE_OWNER,TABLE_NAME,PARTITION_NAME,HIGH_VALUE,NUM_ROWS)
VALUES ('TO','TN','SYS_P201709','TIMESTAMP'' 2019-01-30 00:00:00''',5053133);
SELECT TABLE_OWNER, TABLE_NAME, PARTITION_NAME, HIGH_VALUE, NUM_ROWS
from ALL_TAB_PARTITIONS;

Answer 1

If you are using Oracle 12c you could still use function but defined inline:
WITH FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS
BEGIN
-- logic here
RETURN p_id;
END;
SELECT with_function(id)
FROM your_table
Related: WITH Clause Enhancements in Oracle Database 12c Release 1 (12.1)

Answer 2

For the conversion of a LONG type ( HIGH_VALUE ) to TIMESTAMP,
One option is to use dynamic sql and perform your insert through an anonymous block. No Procedure or function is required.
DECLARE
tstamp TIMESTAMP;
BEGIN
FOR rec IN ( SELECT table_owner,table_name,partition_name,high_value,num_rows
FROM all_tab_partitions
WHERE ROWNUM < 5
) LOOP
EXECUTE IMMEDIATE 'BEGIN :dt := '
|| rec.high_value
|| '; END;'
USING OUT tstamp; --assign the long to an external timestamp variable
INSERT INTO export_table (
table_owner,table_name,partition_name,high_value,num_rows
) VALUES (rec.table_owner,
rec.table_name, rec.partition_name, tstamp, rec.num_rows
);
END LOOP;
END;
/
AS #APC commented, There's also a solution using Pure SQL, which
uses a slightly complex Xml expression.

Answer 3

Combining the pure SQL solution from APC's comment with the enhancements in Oracle 12 to allow functions to be declared in WITH clauses and Kaushik Nayak's method of using EXECUTE IMMEDIATE to convert the string value to a date then you can get this:
Oracle Setup - Test Table & Data:
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 VALUES ( 'TO', 'TN', 'PN', 'TIMESTAMP ''2019-06-26 12:34:56''', 12345 );
Query:
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,
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;
Output:
TABLE_OWNER | TABLE_NAME | PARTITION_NAME | HIGH_VALUE | NUM_ROWS
:---------- | :--------- | :------------- | :------------------ | -------:
TO | TN | PN | 2019-06-26 12:34:56 | 12345
db<>fiddle here
Update: If you want to aggregate some columns then:
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;
db<>fiddle here