src/Leevel/Database/Select.php
public function findSum(string $field, string $alias = 'sum_value', bool $flag = false)
    {
        return $this->findAggregateResult('sum', $field, $alias, $flag);
    }
public function findSum(string $field, string $alias = 'sum_value', bool $flag = false)
    {
        return $this->findAggregateResult('sum', $field, $alias, $flag);
    }
合计

@param string $field
@param string $alias
@param bool   $flag  指示是否不做任何操作只返回 SQL

@return mixed