DateDiff asc and desc - sql

Question

SELECT DISTINCT
at.AccountId AS AccountId,
a.FirstName + ' ' + a.LastName AS [FullName],
DATEDIFF(day, T.ArrivalDate, T.ReturnDate) AS LongestTrip,
DATEDIFF(day, T.ArrivalDate, T.ReturnDate) AS ShortestTrip
FROM
Accounts a
JOIN
AccountsTrips at ON a.Id = AT.AccountId
JOIN
Trips t ON T.Id = AT.TripId
WHERE
a.MiddleName IS NULL AND t.CancelDate IS NULL
ORDER BY
DATEDIFF(day, T.ArrivalDate, T.ReturnDate) DESC, ShortestTrip ASC
The code only orders the tables descending in LongestTrip and in ShortestTrip
SAMPLE DATA !
Find the longest and shortest trip for each account, in days. Filter the results to accounts with no middle name and trips, which are not cancelled (CancelDate is null).
Order the results by Longest Trip days (descending), then by Shortest Trip (ascending).
Examples
AccountId FullName LongestTrip ShortestTrip
------------------------------------------------------------
40 Winna Maisey 7 1
56 Tillie Windress 7 1
57 Eadith Gull 7 1
66 Sargent Rockhall 7 1
69 Jerome Flory 7 2
… … … …
The Tables are --
CREATE TABLE Cities
(
Id INT PRIMARY KEY IDENTITY,
Name NVARCHAR(20) NOT NULL,
CountryCode CHAR(2) NOT NULL
)
CREATE TABLE Hotels
(
Id INT PRIMARY KEY IDENTITY,
Name NVARCHAR(30) NOT NULL,
CityId INT FOREIGN KEY REFERENCES Cities(Id) NOT NULL,
EmployeeCount INT NOT NULL,
BaseRate DECIMAL(10,2)
)
CREATE TABLE Rooms
(
Id INT PRIMARY KEY IDENTITY,
Price DECIMAL(10,2) NOT NULL,
Type NVARCHAR(20) NOT NULL,
Beds INT NOT NULL,
HotelId INT FOREIGN KEY REFERENCES Hotels(Id) NOT NULL
)
CREATE TABLE Trips
(
Id INT PRIMARY KEY IDENTITY,
RoomId INT FOREIGN KEY REFERENCES Rooms(Id) NOT NULL,
BookDate DATE NOT NULL, CHECK(BookDate<ArrivalDate),
ArrivalDate DATE NOT NULL, CHECK(ArrivalDate<ReturnDate),
ReturnDate DATE NOT NULL,
CancelDate DATE
)
CREATE TABLE Accounts
(
Id INT PRIMARY KEY IDENTITY,
FirstName NVARCHAR(50) NOT NULL,
MiddleName NVARCHAR(20),
LastName NVARCHAR(50) NOT NULL,
CityId INT NOT NULL,
BirthDate DATE NOT NULL,
Email VARCHAR(100) UNIQUE NOT NULL
CONSTRAINT FK_CityId FOREIGN KEY (CityId)
REFERENCES Cities(Id)
)
CREATE TABLE AccountsTrips
(
AccountId INT FOREIGN KEY REFERENCES Accounts(Id) NOT NULL,
TripId INT FOREIGN KEY REFERENCES Trips(Id) NOT NULL,
Luggage INT NOT NULL, CHECK(Luggage >= 0)
)

Answer 1

You want to pick the longest and shortest trips per account from your data. As all you want to get from the trips is the duration, you can simply aggregate and show MIN and MAX duration:
SELECT
a.Id AS AccountId,
a.FirstName + ' ' + a.LastName AS [FullName],
MIN(DATEDIFF(day, T.ArrivalDate, T.ReturnDate)) AS LongestTrip,
MAXD(ATEDIFF(day, T.ArrivalDate, T.ReturnDate)) AS ShortestTrip
FROM
Accounts a
JOIN
AccountsTrips at ON a.Id = AT.AccountId
JOIN
Trips t ON T.Id = AT.TripId
WHERE
a.MiddleName IS NULL AND t.CancelDate IS NULL
GROUP BY
a.Id, a.FirstName, a.LastName
ORDER BY
LongestTrip DESC, ShortestTrip ASC;
If you wanted to show additional data from the trips, you would use window functions (probably MIN OVER and MAX OVER) and would then either show two rows per account or aggregate these two rows.