How to use select statement insert first row of dummy dash value with 2 table combination

Question

table_A
no   desciption         
1     Apple
2     orange
3     banana
4     kiwi
5     papaya

table_B
no     price      mydate
1      10.00      20210801
2       8.00      20210802
3       5.00      20210803
4      12.00      20210804
5       4.00      20210805

Hi, I try to use this SQL and union all but show an error.

select '-' a.description, '-' b.price from dual union all select a.description,sum(b.price) from table_A a, table_B b where a.no=b.no and b.mydate='20210801' group by a.description;

ORA-00923 : FROM keyword not found where expected

I need result

a.description    sum(b.price)
   -                  -       <-----dummy dash always on first row
   Apple            10.00

Anyone help is much appreciated.

Answer 1

1. There is no aliases a and b in your first part of union all, so just remove a. and b.
2. Don't use implicit conversion from char literals to date, use literal dates instead:

select '-' as description, '-' as price from dual 
union all 
select a.description,to_char(sum(b.price))
from 
    table_A a
    join table_B b 
        on a.no=b.no
where b.mydate=date'2021-08-01' 
group by a.description;