Thanks for the question, Ken.

Asked: January 09, 2018 - 6:05 pm UTC

Last updated: January 10, 2018 - 4:47 am UTC

Version: Oracle Database 12c Standard Edition Release 12.1.0.2.0 - 64bit Production

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You Asked

If I use the tilde to escape an underscore in SQL it works fine:

select x from
(
select 'A_Babc' x from dual
union all
select 'A$Bxyz' x from dual
)
where x like 'A~_B%' escape '~'

X
------
A_Babc

However, when using the backslash to escape it, I get an error:
select x from
(
select 'A_Babc' x from dual
union all
select 'A$Bxyz' x from dual
)
where x like 'A\_B%' escape '\'

Error report -
SQL Error: ORA-01425: escape character must be character string of length 1
01425. 00000 - "escape character must be character string of length 1"
*Cause: Given escape character for LIKE is not a character string of
length 1.
*Action: Change it to a character string of length 1.

This makes me suspect that this feature is not reliable - period!

I welcome your feedback,
Ken

and Connor said...

I can't reproduce that on any database I have

SQL> select banner from v$version where rownum = 1;

BANNER
-----------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

1 row selected.

SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A~_B%' escape '~';

X
------
A_Babc

1 row selected.

SQL>
SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A\_B%' escape '\';

X
------
A_Babc

1 row selected.

SQL> select banner from v$version where rownum = 1;

BANNER
------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A~_B%' escape '~';

X
------
A_Babc

SQL>
SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A\_B%' escape '\';

X
------
A_Babc

SQL> select banner from v$version where rownum = 1;

BANNER
-----------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A~_B%' escape '~';

X
------
A_Babc

SQL>
SQL>
SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A\_B%' escape '\';

X
------
A_Babc

Are you sure that you don't have an errant space in there anywhere ? eg

SQL> select x from
  2  (
  3  select 'A_Babc' x from dual
  4  union all
  5  select 'A$Bxyz' x from dual
  6  )
  7  where x like 'A\_B%' escape '\ ';   -- trailing space
where x like 'A\_B%' escape '\ '
                            *
ERROR at line 7:
ORA-01425: escape character must be character string of length 1

or running it in some environment where the backslash is special to the environment itself (eg unix shell)

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