SQL Oracle - display values only once per column - sql

Question

I'm trying to format a select statement. The assignment specifies that it has to be formatted this way.
I have a database regarding a taxi service. I have to put together a view with the company name, passenger name, and taxi number. Easy. However, the output specifies that the company name should only appear once in the output, at the top of it's own group. So I have:
CREATE VIEW TAXITRIPS(COMPANYNAME, PASSENGERNAME, TAXI#) AS
(SELECT COMPANY.NAME, BOOKING.NAME, VEHICLES.TAXI#
FROM BOOKING JOIN VEHICLES ON BOOKING.TAXI# = VEHICLES.TAXI#
RIGHT OUTER JOIN COMPANY ON VEHICLES.NAME = COMPANY.NAME);
The right outer join is so that companies with no booking recorded are still displayed. If I now run:
SELECT * FROM TAXITRIPS ORDER BY COMPANYNAME ASC;
It will give me something like
COMPANYNAME PASSENGERNAME TAXI#
---------------------------------------------
ABC TAXIS DAVE 192
LEGION CABS
PREMIER CABS SHANE 2154
PREMIER CABS TIM 2169
SILVER SERVICE DAVE 18579
SILVER SERVICE TIM 18124
SILVER SERVICE AARON 18917
No result for legion cabs, all field displayed, et cetera. Assignment specification says it has to look like this.
COMPANYNAME PASSENGERNAME TAXI#
---------------------------------------------
ABC TAXIS DAVE 192
LEGION CABS
PREMIER CABS SHANE 2154
TIM 2169
SILVER SERVICE DAVE 18579
TIM 18124
AARON 18917
The company name should only be displayed on its first row. DISTINCT is not helping. Any advice?

Answer 1

Normally, you would do this at the application layer, because the result set relies on the ordering of the rows -- a bad thing in SQL.
But you can do it as:
SELECT (CASE WHEN ROW_NUMBER() OVER (PARTITION BY c.NAME ORDER BY v.TAXI#) = 1
THEN c.NAME
END) as CompanyName, b.NAME, v.TAXI#
FROM COMPANY c LEFT JOIN
VEHICLES v
ON v.NAME = c.NAME LEFT JOIN
BOOKING b
ON b.TAXI# = v.FLIGHT#
ORDER BY c.name, v.taxi#;
Note: I rearranged the joins to be LEFT JOINs. Most people find that easier to follow than RIGHT JOINs.