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String parsing in PL/SQL: how to produce a list using "double-asterisk" separated fields in a VARCHAR2.

Posted on 2008-10-06
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Last Modified: 2013-12-18
Please assume you have the following string, stored in a VARCHAR2(4000):

ASTRING = '**NE**NECOLL1**NECOLL2**NE37509999**';

Using double-asterisk (==> **) as separator, I would like to write a VIEW script:

CREATE OR REPLACE VIEW STRING_SPLITTER AS SELECT ...........

The VIEW STRING_SPLITTER has to produce the following output, if SELECTed:

SELECT * FROM STRING_SPLITTER;

NE
NECOLL1
NECOLL2
NE37509999
4 row(s) selected

Any clues?!
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Question by:CRISTIANO_CORRADI
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Shaju Kumbalath earned 500 total points
ID: 22648800
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by:CRISTIANO_CORRADI
ID: 22648894
Perfect!
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Author Comment

by:CRISTIANO_CORRADI
ID: 22648902
I've customized, for my application, the following solution found in the suggested hypertextual link:


Using a Pipelined Function
An alternative to a standard PL/SQL function (from 9i onwards) is the use of pipelined functions. 
SQL> CREATE TYPE test_type AS TABLE OF VARCHAR2(100);
  2  /
 
Type created.
 
SQL> CREATE OR REPLACE FUNCTION f_convert2(p_list IN VARCHAR2)
  2    RETURN test_type
  3  PIPELINED
  4  AS
  5    l_string       LONG := p_list || ',';
  6    l_comma_index  PLS_INTEGER;
  7    l_index        PLS_INTEGER := 1;
  8  BEGIN
  9    LOOP
 10      l_comma_index := INSTR(l_string, ',', l_index);
 11      EXIT WHEN l_comma_index = 0;
 12      PIPE ROW ( SUBSTR(l_string, l_index, l_comma_index - l_index) );
 13      l_index := l_comma_index + 1;
 14    END LOOP;
 15    RETURN;
 16  END f_convert2;
 17  /
 
Function created.
 
SQL> SELECT * FROM TABLE(f_convert('AAA,BBB,CCC,D'));
 
COLUMN_VALUE
--------------------------------------------------------------------------------
AAA
BBB
CCC
D
 
4 rows selected.
The advantage of pipelined functions is that the PIPE ROW statement means that the whole collection is not populated all at once, as in Table Functions. In that respect, it is much more memory efficient. 

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Author Closing Comment

by:CRISTIANO_CORRADI
ID: 31503358
Thank you very much for your kind cooperation.
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Expert Comment

by:Shaju Kumbalath
ID: 22648916

select answer
from (
select trim(substr(str, instr(str, '**', 1, level) + 2,
instr(str, '**', 1, level + 1) - instr(str, '**', 1, level) - 2)) answer
, level lv
, lag(level, 1, 0) over (order by level) lg
from (
select '**NE**NECOLL1**NECOLL2**NE37509999**' str
from dual)
connect by instr(str, '**', 1, level) > 0)
where answer is not null
and lv != lg;  
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