How to write nested query in select?

Question

Oracle

There is a need for this query:

select (select sum(rashody) from transport_reestr where transport_type=‘taxi’)/ sum(rashody) from transport_reestr

Gives an error not single group group function, although grouping is not needed here and the sum goes over all columns

Answer 1

Need to add GROUP BY

SELECT (SELECT SUM (RASHODY)
          FROM TRANSPORT_REESTR
         WHERE TRANSPORT_TYPE = 'TAXI') / SUM (RASHODY)
  FROM TRANSPORT_REESTR
  GROUP BY НАЗВАНИЕ_ПОЛЯ;

Apparently you were trying to portray this?

SELECT (SELECT SUM (RASHODY)
            FROM TRANSPORT_REESTR
           WHERE TRANSPORT_TYPE = 'TAXI') / 
         (SELECT SUM (RASHODY) 
            FROM TRANSPORT_REESTR)
    FROM DUAL;