SELECT DISTINCT very slow

Question

hi @all
I'm using Oracle 11g R2 on Windows 7
Unfortunately i have a column in a table that stored multiple vales delimited with *,* e.g. [+*execute 1B-B-06-34-61-00A-281A-A, 1B-B-06-37-10-00A-281A-A, 1B-B-06-37-20-00A-281A-A, 1B-B-06-37-30-00A-281A-A*+]
I have to query that column to get seperate values after execute
Example:
Serial_No Remarks
---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
AS0007 execute 1B-B-06-34-61-00A-281A-A, 1B-B-06-37-10-00A-281A-A, 1B-B-06-37-20-00A-281A-A, 1B-B-06-37-30-00A-281A-A
---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
AS0007 execute 1B-B-28-52-00-00A-340C-A
---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
AS0007 execute 1B-B-57-11-03-06A-281A-A, 1B-B-57-11-03-07A-281A-A, 1B-B-57-11-03-07B-281A-A,
---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
expected Output:
Serial_No Remarks
---------|----------------------------------------------------------------
AS0007 1B-B-06-34-61-00A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-06-37-10-00A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-06-37-20-00A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-06-37-30-00A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-28-52-00-00A-340C-A
---------|----------------------------------------------------------------
AS0007 1B-B-57-11-03-06A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-57-11-03-07A-281A-A
---------|----------------------------------------------------------------
AS0007 1B-B-57-11-03-07B-281A-A
I have the following Script to query this:
select distinct SCHED_MAINT.AC_SERIAL_NO, regexp_substr (SUBSTR(SCHED_MAINT.Remarks, 9), '[^,]+', 1, level) as DMC
from SCHED_MAINT
where SCHED_MAINT.NEXT_DUE_MINS = '24000'
and SCHED_MAINT.AC_SERIAL_NO = 'AS0007'
connect by prior SCHED_MAINT.AC_SERIAL_NO = SCHED_MAINT.AC_SERIAL_NO
and regexp_instr (SCHED_MAINT.Remarks, '[^,]+', 1, level) > 0
and prior dbms_random.string ('p', 10) is not null;
The Problem is that, with this few rows it works, but slow, if i have more rows e.g 1000, I killed the runtime after 2h without any output
If I run this script without the DISTINCT it runs fast in one second but i get duplicated rows
any suggestions to solve this problem
unfortunately i cannot use funktions or procedures
thanks in advanced
cu ice

Answer 1

WITH clause is just aon-the-fly sample of your real table. Simply remove WITH clause and run:
select  distinct ac_serial_no,
                 trim(regexp_substr(remarks,'[^,]+',9,column_value)) as DMC
  from  sched_maint,
        table(
              cast(
                   multiset(
                            select  level
                              from  dual
                              connect by level < regexp_count(remarks,',',9) + 1
                   as sys.OdciNumberList
/ And it would take you less time to test multiple ac_serial_no than to post the question:
with sched_maint as (
                     select 'AS0007' ac_serial_no,'execute 1B-B-06-34-61-00A-281A-A, 1B-B-06-37-10-00A-281A-A, 1B-B-06-37-20-00A-281A-A, 1B-B-06-37-30-00A-281A-A' remarks from dual union all
                     select 'AS0007','execute 1B-B-28-52-00-00A-340C-A' from dual union all
                     select 'AS0007','execute 1B-B-57-11-03-06A-281A-A, 1B-B-57-11-03-07A-281A-A, 1B-B-57-11-03-07B-281A-A' from dual union all
                     select 'AS0008' ac_serial_no,'execute 1B-B-06-34-61-00A-281A-A, 1B-B-06-37-10-00A-281A-A, 1B-B-06-37-20-00A-281A-A, 1B-B-06-37-30-00A-281A-A' remarks from dual union all
                     select 'AS0008','execute 1B-B-28-52-00-00A-340C-A' from dual union all
                     select 'AS0008','execute 1B-B-57-11-03-06A-281A-A, 1B-B-57-11-03-07A-281A-A, 1B-B-57-11-03-07B-281A-A' from dual
select  distinct ac_serial_no,
                 trim(regexp_substr(remarks,'[^,]+',9,column_value)) as DMC
  from  sched_maint,
        table(
              cast(
                   multiset(
                            select  level
                              from  dual
                              connect by level < regexp_count(remarks,',',9) + 1
                   as sys.OdciNumberList
AC_SER DMC
AS0007 1B-B-06-34-61-00A-281A-A
AS0007 1B-B-06-37-10-00A-281A-A
AS0007 1B-B-06-37-20-00A-281A-A
AS0007 1B-B-28-52-00-00A-340C-A
AS0007 1B-B-57-11-03-06A-281A-A
AS0007 1B-B-57-11-03-07A-281A-A
AS0008 1B-B-06-34-61-00A-281A-A
AS0008 1B-B-06-37-10-00A-281A-A
AS0008 1B-B-06-37-20-00A-281A-A
AS0008 1B-B-28-52-00-00A-340C-A
AS0008 1B-B-57-11-03-06A-281A-A
AC_SER DMC
AS0008 1B-B-57-11-03-07A-281A-A
12 rows selected.
SQL> SY.