Avoid Unions to get TOP count - sql

Question

Here are two tables:
LocationId Address City State Zip
1 2100, 1st St Austin TX 76819
2 2200, 2nd St Austin TX 76829
3 2300, 3rd St Austin TX 76839
4 2400, 4th St Austin TX 76849
5 2500, 5th St Austin TX 76859
6 2600, 6th St Austin TX 76869
TripId PassengerId FromLocationId ToLocationId
1 746896 1 2
2 746896 2 1
3 234456 1 3
4 234456 3 1
5 234456 1 4
6 234456 4 1
7 234456 1 6
8 234456 6 1
9 746896 1 2
10 746896 2 1
11 746896 1 2
12 746896 2 1
I want TOP 5 locations which each passenger has traveled to (does not matter if its from or to location). I can get it using a UNION, but was wondering if there was a better way to do this.
My Solution:
select top 5 *
from
(select count(l.LocationId) as cnt, l.LocationId, l.Address1, l.Address2, l.City, St.State , l.Zip
from
Trip t
join LOCATION l on t.FromLocationId = l.LocationId
where t.PassengerId = 746896
group by count(l.LocationId) as cnt, l.LocationId, l.Address1, l.Address2, l.City, St.State , l.Zip
UNION
select count(l.LocationId) as cnt, l.LocationId, l.Address1, l.Address2, l.City, St.State , l.Zip
from
Trip t
join LOCATION l on t.ToLocationId = l.LocationId
where t.PassengerId = 746896
group by count(l.LocationId) as cnt, l.LocationId, l.Address1, l.Address2, l.City, St.State , l.Zip
) as tbl
order by cnt desc

Answer 1

This will give you top 5 location.
SELECT TOP 5 tmp.fromlocationid AS locationid,
Count(tmp.fromlocationid) AS Times
FROM (SELECT fromlocationid
FROM trip
UNION ALL
SELECT tolocationid
FROM trip) tmp
GROUP BY tmp.fromlocationid
Method 1: This will give you top 5 location of each passenger.
WITH cte AS
( SELECT passengerid,
locationid,
Count(locationid) AS Times,
Row_number() OVER(partition BY passengerid ORDER BY passengerid ASC) AS RowNum
FROM (SELECT tripid, passengerid, fromlocationid AS locationid
FROM trip
UNION ALL
SELECT tripid, passengerid, tolocationid AS locationid
FROM trip) tmp
GROUP BY passengerid, locationid )
SELECT *
FROM cte
WHERE rownum <= 5
ORDER BY passengerid, Times DESC
Method 2: Same result without Union Operator (Top 5 location of each passenger)
WITH cte AS
( SELECT passengerid,
locationid,
Count(locationid) AS Times,
Row_number() OVER(partition BY passengerid ORDER BY passengerid ASC) AS RowNum
FROM trip
UNPIVOT ( locationid
FOR subject IN (fromlocationid, tolocationid) ) u
GROUP BY passengerid, locationid )
SELECT *
FROM cte
WHERE rownum <= 5
ORDER BY passengerid, times DESC
If you also want to get the location details, you can simply join the location table.
SELECT cte.* , location.*
FROM cte
INNER JOIN location ON location.locationid = cte.locationid
WHERE rownum <= 5
ORDER BY passengerid, times DESC
Reference
- https://stackoverflow.com/a/19056083/6327676

Answer 2

YOou'll need to replace the SELECT *'s with the columns you need, however, something like this should work:
WITH Visits AS (
SELECT *,
COUNT(*) OVER (PARTITION BY t.PassengerID, L.LocationID) AS Visits
FROM Trip T
JOIN [Location] L ON T.FromLocationId = L.LocationId),
Rankings AS (
SELECT *,
DENSE_RANK() OVER (PARTITION BY V.PassengerID ORDER BY Visits DESC) AS Ranking
FROM Visits V)
SELECT *
FROM Rankings
WHERE Ranking <= 5;

Answer 3

Further simplified solution
select top 3 * from
(
Select distinct count(locationId) as cnt, locationId from trip
unpivot
(
locationId
for direction in (fromLocationId, toLocationId)
)u
where passengerId IN (746896, 234456)
group by direction, locationId
)as tbl2
order by cnt desc;
Solution combining columns
The main issue for me is avoiding union to combine the two columns.
The UNPIVOT command can do this.
select top 3 * from (
select count(locationId) cnt, locationId
from
(
Select valu as locationId, passengerId from trip
unpivot
(
valu
for loc in (fromLocationId, toLocationId)
)u
)united
where passengerId IN (746896, 234456)
group by locationId
) as tbl
order by cnt desc;
http://sqlfiddle.com/#!18/cec8b/136
If you want to get the counts by direction:
select top 3 * from (
select count(locationId) cnt, locationId, direction
from
(
Select valu as locationId, direction, passengerId from trip
unpivot
(
valu
for direction in (fromLocationId, toLocationId)
)u
)united
where passengerId IN (746896, 234456)
group by locationId, direction
) as tbl
order by cnt desc;
http://sqlfiddle.com/#!18/cec8b/139
Same Results as you ( minus some minor descriptions )
select top 3 * from
(
select distinct * from (
select count(locationId) cnt, locationId
from
(
Select valu as locationId, direction, passengerId from trip
unpivot
(
valu
for direction in (fromLocationId, toLocationId)
)u
)united
where passengerId IN (746896, 234456)
group by locationId, direction
) as tbl
)as tbl2
order by cnt desc;

Answer 4

You can do this without union all:
select top (5) t.passengerid, v.locationid, count(*)
from trip t cross apply
(values (fromlocationid), (tolocationid)) v(locationid) join
location l
on v.locationid = l.locationid
where t.PassengerId = 746896
group by t.passengerid, v.locationid
order by count(*) desc;
If you want an answer for all passengers, it would be a similar idea, using row_number(), but your query suggests you want the answer only for one customer at a time.
You can include additional fields from location as well.
Here is a SQL Fiddle.