UPPER() et BINARY_CI peuvent produire les mêmes résultats mais Oracle ne peut pas les utiliser de manière interchangeable. Pour utiliser un index et BINARY_CI, vous devez créer un index comme celui-ci :
create index src_nlssort_index on src(nlssort(b, 'nls_sort=''BINARY_CI'''));
Exemple de tableau et données de cas mixtes
create table src(b varchar2(100) not null);
insert into src select 'MiXeD CAse '||level from dual connect by level <= 100000;
Par défaut, le prédicat upper() peut effectuer une analyse de plage sur l'index upper()
create index src_upper_index on src(upper(b));
explain plan for
select * from src where upper(b) = 'MIXED CASE 1';
select * from table(dbms_xplan.display(format => '-rows -bytes -cost -predicate
-note'));
Plan hash value: 1533361696
------------------------------------------------------------------
| Id | Operation | Name | Time |
------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| SRC | 00:00:01 |
| 2 | INDEX RANGE SCAN | SRC_UPPER_INDEX | 00:00:01 |
------------------------------------------------------------------
BINARY_CI et LINGUISTIC n'utiliseront pas l'index
alter session set nls_sort='binary_ci';
alter session set nls_comp='linguistic';
explain plan for
select * from src where b = 'MIXED CASE 1';
select * from table(dbms_xplan.display(format => '-rows -bytes -cost -note'));
Plan hash value: 3368256651
---------------------------------------------
| Id | Operation | Name | Time |
---------------------------------------------
| 0 | SELECT STATEMENT | | 00:00:02 |
|* 1 | TABLE ACCESS FULL| SRC | 00:00:02 |
---------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(NLSSORT("B",'nls_sort=''BINARY_CI''')=HEXTORAW('6D69786564
2063617365203100') )
L'index basé sur la fonction sur NLSSORT() permet des analyses de plage d'index
create index src_nlssort_index on src(nlssort(b, 'nls_sort=''BINARY_CI'''));
explain plan for
select * from src where b = 'MIXED CASE 1';
select * from table(dbms_xplan.display(format => '-rows -bytes -cost -note'));
Plan hash value: 478278159
--------------------------------------------------------------------
| Id | Operation | Name | Time |
--------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| SRC | 00:00:01 |
|* 2 | INDEX RANGE SCAN | SRC_NLSSORT_INDEX | 00:00:01 |
--------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access(NLSSORT("B",'nls_sort=''BINARY_CI''')=HEXTORAW('6D69786564
2063617365203100') )
