CHR(0) in REGEXP_LIKE

Question

I am using the queries to check how chr(0) behaves in regexp_like.

CREATE TABLE t1(a char(10));
INSERT INTO t1 VALUES(\'0123456789\');
SELECT CASE WHEN REGE         


        

Answer 1

Not an answer, just some experiments, but too long for a comment.

REGEXP_COUNT seems to be confused by chr(0), counting every character as chr(0); besides, it seems to find one occurrence more than the size of the string.

SQL> select dump('a'), regexp_count('a', chr(0)) from dual;

DUMP('A')        REGEXP_COUNT('A',CHR(0))
---------------- ------------------------
Typ=96 Len=1: 97                        2

SQL> select dump(chr(0)), regexp_count(chr(0), chr(0)) from dual;

DUMP(CHR(0))   REGEXP_COUNT(CHR(0),CHR(0))
-------------- ---------------------------
Typ=1 Len=1: 0                           2

SQL> select dump('0123456789' || chr(0)), regexp_count('0123456789' || chr(0), chr(0)) from dual;

DUMP('0123456789'||CHR(0))                    REGEXP_COUNT('0123456789'||CHR(0),CHR(0))
--------------------------------------------- -----------------------------------------
Typ=1 Len=11: 48,49,50,51,52,53,54,55,56,57,0                                        12

LIKE seems to have a good behaviour, while its REGEXP version seems to fail:

SQL> select 1 from dual where 'a' like '%' || chr(0) || '%';

no rows selected

SQL> select 1 from dual where regexp_like ('a', chr(0));

         1
----------
         1

Same thing for INSTR and REGEXP_INSTR

SQL> select 1 from dual where instr('a', chr(0)) != 0;

no rows selected

SQL> select 1 from dual where regexp_instr('a', chr(0)) != 0;

         1
----------
         1

Tested on 11g XE Release 11.2.0.2.0 - 64bit