SQLSTATE[42000]: Syntax error or access violation: 1055 'avanthi_erp.purchases.supplier_id' isn't in GROUP BY code example

Example: syntax error or access violation: 1055 'database.table.id' isn't in GROUP BY

Short answer : 
==================
1. In config\database.php --> "mysql" array

2. Set 'strict' => false to disable all.

=---------------- or ----------------------------=
You can leave 'strict' => true and add modes to "mysql" option in

'mysql' => [
       ...
       ....
       'strict' => true,
       'modes' => [
            //'ONLY_FULL_GROUP_BY', // Disable this to allow grouping by one column
            'STRICT_TRANS_TABLES',
            'NO_ZERO_IN_DATE',
            'NO_ZERO_DATE',
            'ERROR_FOR_DIVISION_BY_ZERO',
            'NO_AUTO_CREATE_USER',
            'NO_ENGINE_SUBSTITUTION'
        ],
 ]
 
Detailed answer :
==================
You may not need to disable all strict options ... Kindly have a look on this
answer about this issue. 
Link : https://github.com/laravel/framework/issues/14997#issuecomment-242129087