Order and filter follow different criteria in Oracle? - oracle

Question

I'm having a problem while trying to apply a filter in an Oracle (12.2.0.1.0) query.
When I query for the values of a column in a table using order by that same column, I get
75A0000000
7597953181
7597953182
But then, when I try to filter the rows with the column between the first and the last value I'm not getting results at all.
This works perfectly fine if the column has only numeric values, but it gets it all wrong when there is some alphabetic value in the middle.
It seems like Oracle is following the criteria A<0 when ordering a result but A>0 when filtering that result.
This can be reproduced using this query:
select * from (
WITH DATA AS
(SELECT '1, A, 2' str FROM dual)
SELECT trim(regexp_substr(str, '[^,]+', 1, LEVEL)) str
FROM DATA
CONNECT BY instr(str, ',', 1, LEVEL - 1) > 0)
where str>='1' and str<='A'
order by str
The result of this query is
A
1
2
that should mean A is less than 1, but the filter applied to make it return some values is just the opposite : str values greater or equal than 1 and less or equal than A.
Anybody knows why? Thanks in advance.

Answer 1

To me, it looks as if it is about binary or linguistic sort.
Sample data:
SQL> select * from test;
C
-
1
A
2
Sort by col, as is:
SQL> select col, ascii(col)
2 from test
3 order by col;
C ASCII(COL)
- ----------
A 65
1 49
2 50
Or, sort by col's ASCII code:
SQL> select col, ascii(col)
2 from test
3 order by ascii(col);
C ASCII(COL)
- ----------
1 49
2 50
A 65
Explicitly stating binary or linguistic sort:
SQL> select col
2 from test
3 order by nlssort(col, 'nls_sort=binary'); --> binary
C
-
1
2
A
SQL> select col
2 from test
3 order by nlssort(col, 'nls_sort=croatian'); --> linguistic
C
-
A
1
2
SQL>
Or, alter session and set nls_sort you want:
SQL> alter session set nls_sort='binary';
Session altered.
SQL> select * From test order by col;
C
-
1
2
A
SQL>
If you get unexpected result, check what's nls_sort set in your session:
SQL> select * from nls_session_parameters where parameter = 'NLS_SORT';
PARAMETER VALUE
------------------------------ ----------------------------------------
NLS_SORT BINARY
SQL>
Using your query:
SQL> select * from (
2 WITH DATA AS
3 (SELECT '1, A, 2' str FROM dual)
4 SELECT trim(regexp_substr(str, '[^,]+', 1, LEVEL)) str
5 FROM DATA
6 CONNECT BY instr(str, ',', 1, LEVEL - 1) > 0)
7 where str>='1' and str<='A'
8 order by nlssort(str, 'nls_sort=binary'); --> this
STR
-------
1
2
A
SQL>