Oracle Escape Characters:oracle 跳脫字符

時間 2019-11-11

標籤 oracle escape characters 字符欄目 Oracle 简体版

原文原文鏈接

1、Oracle 對於查詢中間的的一些特殊字符，若是讓它按照字面上去解釋而不是看成特殊字符呢java

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.sql

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:session

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

KSPPINM this

-------------------------------- spa

sessions code

license_max_sessions orm

license_sessions_warning ci

_session_idle_bit_latches rem

_enable_NUMA_optimization underscore

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

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