Exploit database error to leak users data ( Error based sql injection )

Hi everybody I don’t post much write-ups online because most of the work done privately and under NDA. But this time i decided to publish this (anonymously after website owner agreed ) because too many developers insists that you can’t exploit complicated SQL , or non result SQL (example: count(*) sql). Note: You can automate everything in this article using SQLMap, but i choose to exploit it manually to explain under the hood proccess.