Oracle Escape Characters: oracle 점프 문자

1. Oracle 은 중간 에 있 는 특수 문 자 를 조회 하 는 데 있어 서 특수 문자 가 아 닌 글자 로 해석 하도록 한다 면?
Oracle allows the assignment of special escape characters to tell Oracle that the character is interpreted literally.  Certain characters such as the underscore ?_? are not interpreted literally because they have special meaning within Oracle.
In the example below, we want to find all Oracle parameter that relate to I/O, so we are tempted to use the filter LIKE  ?%_io_%?.  Below we will select from the x$ksppi fixed table, filtering with the LIKE clause:

select ksppinm 
from x$ksppi 
where ksppinm like '%_io_%';

 
KSPPINM                                                                        
--------------------------------           
sessions                                                                        
license_max_sessions                                                           
license_sessions_warning                                                       
_session_idle_bit_latches                                                       
_enable_NUMA_optimization                                                      
java_soft_sessionspace_limit                                                   
java_max_sessionspace_size                                                     
_trace_options                                                                 
_io_slaves_disabled                                                            
dbwr_io_slaves                                                                 
_lgwr_io_slaves
As you can see above, we did not get the answer we expected.  The SQL displayed all values that contained ?io?, and not just those with an underscore.  To remedy this problem, Oracle SQL supports an ESCAPE clause to tell Oracle that the character is to be interpreted literally:

select ksppinm 
from x$ksppi 
where ksppinm like '%\_io\_%' ESCAPE '\';

 
KSPPINM                                                                        
--------------------------------------           
_io_slaves_disabled                                                            
dbwr_io_slaves                                                                 
_lgwr_io_slaves                                                                
_arch_io_slaves                                                                
_backup_disk_io_slaves                                                         
backup_tape_io_slaves                                                          
_backup_io_pool_size                                                            
_db_file_direct_io_count                                                       
_log_io_size                                                                   
fast_start_io_target                                                            
_hash_multiblock_io_count                                                      
_smm_auto_min_io_size                                                          
_smm_auto_max_io_size                                                           
_ldr_io_size