Laravel join tables and concatenate rows - mysql

Question

So I have two tables, organizations and contacts. Both tables have column "email", what I need to do is to keep the name of organization, but in email column concatenate all emails (organization's + all contact emails).
Here are some versions that I tried with no luck
1) this one doesn't group:
$customers = DB::table('customers')
->whereRaw('LENGTH(customers.email) > 4')
->select([
'customers.id',
'customers.name',
'customers.email'
]);
$contacts = DB::table('contacts')
->whereRaw('LENGTH(contacts.email) > 4')
->leftJoin('customers', 'contacts.customer_id', '=', 'customers.id')
->select([
'customers.id',
'customers.name',
'contacts.email'
]);
return $customers
->union($contacts)
->select([
'id',
'name',
DB::raw('GROUP_CONCAT(DISTINCT email, ", ") AS emails'),
])
->groupBy('id')
->get();
2) this one is actually pretty close, but it doesn't filter out entries where neither contact or customer entires have DB::raw('LENGTH(email) > 4')
return $customers = DB::table('customers')
->leftJoin('contacts', 'contacts.customer_id', '=', 'customers.id')
->select([
'customers.id',
'customers.name',
'registration',
DB::raw('GROUP_CONCAT(DISTINCT contacts.email, ", ") AS contact_emails'),
'customers.email'
])
->groupBy('customers.id')
->get();
3) I tried to get closer with subqueries (I know it would only filter out contacts with no emails)
3.1) Trying subquery 1 results in error: JoinClause::whereRaw() doesn't exist
return $customers = DB::table('customers')
->leftJoin('contacts', function($join) {
$join->on('contacts.customer_id', '=', 'customers.id')
->whereRaw('LENGTH(email) > 4');
})...
3.2) This one produces the syntax error below:
return $customers = DB::table('customers')
->leftJoin('contacts', function($join) {
$join->on('contacts.customer_id', '=', 'customers.id')
->where(DB::raw('LENGTH(email) > 4'));
})
1/2 PDOException in Connection.php line 333: SQLSTATE[42000]: Syntax
error or access violation: 1064 You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for the
right syntax to use near '? group by customers.id' at line 1
2/2 QueryException in Connection.php line 713: SQLSTATE[42000]: Syntax
error or access violation: 1064 You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for the
right syntax to use near '? group by customers.id' at line 1 (SQL:
select customers.id, customers.name, registration,
GROUP_CONCAT(DISTINCT contacts.email, ", ") AS contact_emails,
customers.email from customers left join contacts on
contacts.customer_id = customers.id and LENGTH(contacts.email)
4 group by customers.id)
3.3) some examples say I should do it this way, but this produces the error Not enough arguments for the on clause.
return $customers = DB::table('customers')
->leftJoin('contacts', function($join) {
$join->on('contacts.customer_id', '=', 'customers.id');
$join->on(DB::raw('LENGTH(contacts.email) > 4'));
})

Answer 1

This works for me. No syntax errors and filters out contacts with length less than 4 characters:
DB::table('customers')
->leftJoin('contacts', function ($join) {
$join->on('contacts.customer_id', '=', 'customers.id')
->where(DB::raw('length(contacts.email)'), '>', 4);
})
->select([
'customers.id',
'customers.name',
DB::raw('group_concat(distinct contacts.email separator ", ") AS contact_emails'),
])
->groupBy('customers.id')
->get();
Tested in Laravel 5.3.26, MySQL 5.6.20 (no strict mode).