Help with SQL queries following migration

Question

Hi there,
I have just migrated from MS SQL Server database to Oracle 10g database using the Oracle SQL Developer.
My application is using JDBC to access the database, and there are heaps of SQL statements that need to be verified and tested. I've found a number of SQL compatibility issues from my testing of the Oracle database and I hope you can help me the following.
1. Case sensitivity
Is it possible to not enforce case sensitivity (by default) when performing a select query?
If this is not possible, all the SQL statements will need to be changed to evaluate column based on uppercase.
2. Trailing white space
Is it possible to not evaluate trailing white space (by default) when performing a select query?
For example, suppose a table column studentNo has trailing spaces (after database migration), e.g. 'A182D '
when performing query - select * from student where studentNo = 'A182D'
no results can be found
3. Issue with Where condition containing with '' = ''
There are quite a number of SQL statements with Where condition containing '' = ''.
For example, the following SQL query doesn't return any results even though there are matching suburb that starts with 'ST'. These types of queries are mostly used in dynamic generated queries.
select * from Address where (suburb like 'ST%') and ('' = '' or country = '')
Any help or advice will be greatly appreciated.
Regards,
Jason Gordon

Answer 1

As justin mentioned setting those NLS parameters will make oracle not to use your regular index. for that you must create a function based index. See example below.
SQL> create index t_idx on t (name)
  2  /
Index created.
SQL> exec dbms_stats.gather_table_stats(user,'T',cascade=>true)
PL/SQL procedure successfully completed.
SQL> explain plan for
  2  select * from t where name = 'karthick'
  3  /
Explained.
SQL> select * from table(dbms_xplan.display)
  2  /
PLAN_TABLE_OUTPUT
Plan hash value: 2946670127
| Id  | Operation        | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |       |     1 |     9 |     1   (0)| 00:00:01 |
|*  1 |  INDEX RANGE SCAN| T_IDX |     1 |     9 |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
   1 - access("NAME"='karthick')
13 rows selected.
SQL> delete from plan_table
  2  /
2 rows deleted.
SQL> alter session set NLS_COMP=ANSI;
Session altered.
SQL> alter session set NLS_SORT=BINARY_CI;
Session altered.
SQL> explain plan for
  2  select * from t where name = 'karthick'
  3  /
Explained.
SQL> select * from table(dbms_xplan.display)
  2  /
PLAN_TABLE_OUTPUT
Plan hash value: 1601196873
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |     9 |     5   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| T    |     1 |     9 |     5   (0)| 00:00:01 |
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
   1 - filter(NLSSORT("NAME",'nls_sort=''BINARY_CI''')=HEXTORAW('6B61727
              46869636B00') )
14 rows selected.
SQL> create index t_idx_1 on t(NLSSORT(name,'NLS_SORT=BINARY_CI'))
  2  /
Index created.
SQL> exec dbms_stats.gather_table_stats(user,'T',cascade=>true)
PL/SQL procedure successfully completed.
SQL> /
create index t_idx_1 on t(NLSSORT(name,'NLS_SORT=BINARY_CI'))
ERROR at line 1:
ORA-00955: name is already used by an existing object
SQL> delete from plan_table
  2  /
2 rows deleted.
SQL> explain plan for
  2  select * from t where name = 'karthick'
  3  /
Explained.
SQL> select * from table(dbms_xplan.display)
  2  /
PLAN_TABLE_OUTPUT
Plan hash value: 2580036035
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |         |     3 |    27 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T       |     3 |    27 |     2   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | T_IDX_1 |     3 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access(NLSSORT("NAME",'nls_sort=''BINARY_CI''')=HEXTORAW('6B6172746869636B00') )Thanks,
Karthick.