Add field which flags first row after Order By - sql

Question

I have a Select statement that looks a bit like this (shortened here as its just selecting fields from an existing table and nothing overly complicated)
SELECT
CASE
WHEN dbo.Account_Inventory.NUMBER IS NULL THEN 'C' + CAST(CAST(dbo.Account_Inventory.CUST_ID AS bigint) AS nvarchar)
WHEN dbo.Account_Inventory.CUST_ID IS NULL THEN 'A' + CAST(CAST(dbo.Account_Inventory.ACCT_NUM AS bigint) AS nvarchar)
ELSE 'M' + CAST(CAST(dbo.Account_Inventory.NUMBER AS bigint) AS varchar)
END AS ID,
CASE...
...FROM
dbo.Account_Inventory LEFT OUTER JOIN dbo.Dorm ON dbo.Account_Inventory.ACCT_NUM = dbo.Dorm.ACCT_NUM
WHERE
(dbo.Account_Inventory.ACCT_CLOSE_DT IS NULL) AND
(CASE
WHEN dbo.Account_Inventory.XYZ = 'Yes' AND dbo.Account_Inventory.BUS_LINE_CDE IN ('BB', 'BBM', 'ABC', 'ABCD') THEN 'ABC'
WHEN dbo.Account_Inventory.XYZ = 'YES' THEN 'EFG'
ELSE dbo.Account_Inventory.GLOBAL_BUSINESS
END IN ('BIG', 'SMAL','ABC'))
ORDER BY
Order By
ID, dbo.Account_Inventory.INT_DAILY_RATE DESC
After this, I want to add a field which will flag the first record (ID field) and mark it as "Unique" and the other records as "na".
Any help is appreciated!

Answer 1

You can use case statement.
case when row_number() over (order by ID, Rate desc) =1 then 'Unique' else 'na'

Answer 2

Here is how I finally made it work
WITH "temp_results" AS (SELECT
CASE
WHEN dbo.Account_Inventory.NUMBER IS NULL THEN 'C' + CAST(CAST(dbo.Account_Inventory.CUST_ID AS bigint) AS nvarchar)
WHEN dbo.Account_Inventory.CUST_ID IS NULL THEN 'A' + CAST(CAST(dbo.Account_Inventory.ACCT_NUM AS bigint) AS nvarchar)
ELSE 'M' + CAST(CAST(dbo.Account_Inventory.NUMBER AS bigint) AS varchar)
END AS ID,
CASE...
*MORE CASE STATEMENTS*
...FROM
dbo.Account_Inventory LEFT OUTER JOIN dbo.Dorm ON dbo.Account_Inventory.ACCT_NUM = dbo.Dorm.ACCT_NUM
WHERE
(dbo.Account_Inventory.ACCT_CLOSE_DT IS NULL) AND
(CASE
WHEN dbo.Account_Inventory.XYZ = 'Yes' AND dbo.Account_Inventory.BUS_LINE_CDE IN ('BB', 'BBM', 'ABC', 'ABCD') THEN 'ABC'
WHEN dbo.Account_Inventory.XYZ = 'YES' THEN 'EFG'
ELSE dbo.Account_Inventory.GLOBAL_BUSINESS
END IN ('BIG', 'SMAL','ABC'))
ORDER BY
ID, dbo.Account_Inventory.INT_DAILY_RATE DESC OFFSET 0 ROWS)
SELECT "Rel ID", "Rel_Name"...
*LIST ALL FIELDS*
...(CASE WHEN ROW_NUMBER() OVER
(PARTITION BY "Rel_ID" ORDER BY Rel_ID, INT_DAILY_RATE desc)=1 THEN 'Unique' ELSE 'na' END) AS "Unique_Rel_Flag" FROM "temp_results"
What I was stuck on the longest is ending the first Order By statement with "OFFSET 0 ROWS". It will not work without that.
ORDER BY
ID, dbo.Account_Inventory.INT_DAILY_RATE DESC OFFSET 0 ROWS)
Hope that helps someone else out down the line!