Laravel: Left join sql error - php

Question

I have written a sql query using Laravel, but I am not understanding, why the error is creating! The codes are given below,
The join operation:
MeetingRoom::select('mr_id')
->leftJoin('meetingroomhistory',function($join)
{
$join->on('country','=',Session::get('country'));
$join->on('location','=',Session::get('location'));
$join->on('building','=',Session::get('building'));
$join->on('floor','=',Session::get('floor'));
$join->on('name_of_mr','=',Session::get('room'));
})
->where('meetingroom.id','=','meetingroomhistory.mr_id')
->get();
The error:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Bangladesh' in
'on clause' (SQL: select `mr_id` from `meetingroom` left join
`meetingroomhistory` on `country` = `Bangladesh` and `location` =
`Dhaka` and `building` = `Uttara` and `floor` = `3` and `name_of_mr` =
`1` where `meetingroom`.`id` = meetingroomhistory.mr_id)
But if I run the query manually to change this syntax `Bangladesh` to "Bangladesh" using phpmyadmin so it runs well and show me the result. Please someone let me know, how can I fix it?

Answer 1

I think you've confused the where part and the join part.
$join->on($x, $y) statements are for connecting your tables together. Both $x and $y should be names of columns in your tables - that is why Laravel is adding backticks to them.
$where() statements are for comparing with values that you supply. Your Session::get() calls indicate that's what you're doing.
Here's a suggested rewrite, but it may need to be tweaked to suit your exact needs.
MeetingRoom::select('mr_id')
->leftJoin('meetingroomhistory', 'meetingroom.id', '=', 'meetingroomhistory.mr_id')
->$where('meetingroom.country','=',Session::get('country'))
->$where('meetingroom.location','=',Session::get('location'))
->$where('meetingroom.building','=',Session::get('building'))
->$where('meetingroom.floor','=',Session::get('floor'))
->$where('meetingroom.name_of_mr','=',Session::get('room'))
->get();
I assumed the country, location, etc. columns are part of the meetingroom table, if not you can just change them to $where('meetingroomhistory.country', ...) and so on instead.
Finally, I'm not sure why you're selecting only one value, but of course, that's up to you. If you need only a single cell, you can use pluck(), and if you need a lot of single results you could do lists().

Answer 2

I think you should try this.
MeetingRoom::select('mr_id')
->join('meetingroomhistory', function($join)
{
$join->on('meetingroom.id','=','meetingroomhistory.mr_id')
->where('meetingroomhistory.country','=',Session::get('country'));
->where('meetingroomhistory.location','=',Session::get('location'));
->where('meetingroomhistory.building','=',Session::get('building'));
->where('meetingroomhistory.floor','=',Session::get('floor'));
->where('meetingroomhistory.name_of_mr','=',Session::get('room'));
})
->get();