Get Minimum and Maximum value per group in SQL Server 2008 R2 - group-by

Question

I need to get amount attached to minimum and maximum date column per grouping by Property_externalID and Lease_ExternalID.
How would I go about doing this?
Example: result should return one row per grouping:
Property_ExternalID Lease_ExternalID Min_Amount Max_Amount
------------------------------------------------------------------
27050 27050-0200 23 .02
Table sample data:
Property_ExternalID Lease_ExternalID PropertyAssetId Date Amount
---------------------------------------------------------------------------
27050 27050-0200 6097 10/1/2017 23
27050 27050-0200 6097 4/1/2019 0.02
27050 27050-0200 6097 4/1/2021 0.02
27050 27050-0200 6097 4/1/2022 0.02
27050 27050-0200 6097 4/1/2023 0.02
27050 27050-0200 6097 4/1/2024 0.02
27050 27050-0200 6097 4/1/2025 0.02
27050 27050-0200 6097 4/1/2027 0.02
27050 27050-0200 6097 4/1/2026 0.02

Answer 1

It is always helpful to provide some basic SQL statement to create the tables and data so that those helping you out can try different things. Like this...
IF OBJECT_ID('tempdb..#Temp', 'U') IS NOT NULL DROP TABLE #Temp;
CREATE TABLE #Temp
(
Property_ExternalID VARCHAR(15),
Lease_ExternalID VARCHAR(15),
PropertyAssetId VARCHAR(15),
Date DATE,
Amount DECIMAL(10, 2)
)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '10/1/2017', 23)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2019', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2021', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2022', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2023', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2024', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2025', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2027', 0.02)
INSERT INTO #Temp VALUES ('27050', '27050-0200', '6097', '04/1/2026', 0.02)
Given that, you need to join from your main table to a subquery where you have determined what the minimum date is for each Property_ExternalID and Lease_ExternalID. Then you need to join to your main table again (since the minimum and maximum values for Date will likely be different) and then to another subquery where you have determined what the maximum date is for each Property_ExternalID and Lease_ExternalID.
Something like this...
SELECT a.Property_ExternalID, a.Lease_ExternalID, a.Amount AS 'Min_Amount', b.Amount AS 'Max_Amount'
FROM #Temp a
INNER JOIN
(
SELECT Property_ExternalID, Lease_ExternalID, MIN(Date) AS MinDate
FROM #Temp
GROUP BY Property_ExternalID, Lease_ExternalID
) x ON a.Property_ExternalID = x.Property_ExternalID AND a.Lease_ExternalID = x.Lease_ExternalID AND a.Date = x.MinDate
INNER JOIN #Temp b ON a.Property_ExternalID = b.Property_ExternalID AND a.Lease_ExternalID = b.Lease_ExternalID
INNER JOIN
(
SELECT Property_ExternalID, Lease_ExternalID, MAX(Date) AS MaxDate
FROM #Temp
GROUP BY Property_ExternalID, Lease_ExternalID
) y ON b.Property_ExternalID = y.Property_ExternalID AND b.Lease_ExternalID = y.Lease_ExternalID AND b.Date = y.MaxDate
Noel

Answer 2

You need to use the MIN and MAX aggregate functions along with a GROUP BY clause. This should work for you...
DECLARE #MyDate AS DATE
-- comment the next line out if you want all dates
SET #MyDate = '04/01/2021'
SELECT Property_ExternalID, Lease_ExternalID, Date, MIN(Amount) AS 'Min_Amount',
MAX(Amount) AS 'Max_Amount'
FROM YourTable
WHERE Date = COALESCE(#MyDate, Date)
GROUP BY Property_ExternalID, Lease_ExternalID, Date
Noel