如何在MySQL中的汇总行中添加值？

Question

我提出了一个查询以获得工资，最后汇总了结果，但我想添加一个文本'Total'。

select which as 'Salaries',  IFNULL(SUM(which1),0)  as actual,IFNULL(SUM(which2),0) As estimated
from(select Type_expenses_table as which, sum(Amount_expenses_table) as which1, null as which2
           From bacci.expenses_table
           WHERE Date_expenses_table >= '2017-01-01'
           AND Date_expenses_table  < '2017-01-01' + INTERVAL 1 YEAR
           AND Categories_table = 'salaries'
           group by Type_expenses_table
          union all

select estimated_type as which, null as which1, sum(estimated_amount) as which2 
           From bacci.estimated_expenses_table
           Where estimated_year = '2017'
           AND Categories = 'salaries'
           group by estimated_type


 ) ae
 group by which with rollup;

我想把Total而不是null