Laravel - 算术运算

Question

I am trying to calculate two columns values but I am receiving the following error. The Minus between invoice and payment is a arithmetical operation. Can you please help me.

Controller.php

public function getIndex( Request $request )
{
$this->data['balanceTotal'] = \DB::table('tb_accounts')->select('sum(invoice-payment)')->get();
return view('account.index',$this->data);
}

Index.blade.php

{{ $balanceTotal }}

Error

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'sum(invoice-payment)' in 'field list' (SQL: select sum(invoice-payment) from tb_accounts)

Answer 1

You need a raw expression:

\DB::table('tb_accounts')->select(\DB::raw('sum(invoice)'))

But, I suppose you need to sum invoice and payment:

\DB::table('tb_accounts')->select(\DB::raw('(invoice - payment) AS amount'))

See the docs: https://laravel.com/docs/5.5/queries#raw-expressions

Note: avoid the minus in your column name or use back-ticks (Do minus sign in mysql table column names cause issues?)