only_full_group_by

エラー:

OperationalError: (
    1055,
    "Expression #1 of SELECT list is not in GROUP BY clause
    and contains nonaggregated column 'server.sales_sales.sales_status'
    which is not functionally dependent on columns in GROUP BY clause;
    this is incompatible with sql_mode=only_full_group_by")

対処: sql_mod に traditional を指定する

SERVER_DATABASE_URL=mysql://server:password@127.0.0.1:3306/server?sql_mode=traditional