Input the output of one query into second query - sql

Question

I have two sets of queries. First, I calculate the median in seconds to complete transactions for a given period of time. The second query converts the median time retrieved in the first query to date format (DD:HH:MI:SS).
I manually input the output result (calculated median) of the first query into the second query to get my desired result (days hours minutes seconds), this works well. But I wanted a situation where I could combine these two queries into one without manually inputting the time in the second query. See the queries below:
SELECT TxnStartDT, TxnCompleteDT, TxnDuration,
PERCENTILE_CONT(.5) WITHIN GROUP (ORDER BY TxnDuration) OVER() AS MEDIAN
FROM(
SELECT DISTINCT TxnStartDT, TxnCompleteDT,
DATEDIFF(SECOND, TxnStartDT, TxnCompleteDT) AS TxnDuration
FROM MyTable
WHERE (TxnStartDT >='2023-01-02 00:00' and TxnStartDT <= '2023-01-08 23:59') and TxnCompleteDT is not null) AS D
Output
MEDIAN
7333
DECLARE #MD DATETIME = DATEADD(SECOND, 7333, 0)
SELECT --CAST(DATEPART(MONTH, #VARDT) - 1 AS VARCHAR(2)) + ' month(s) '
+ CAST(DATEPART(DAY, #MD) - 1 AS VARCHAR(2)) + ' day(s) '
+ CAST(DATEPART(HOUR, #MD) AS VARCHAR(2)) + ' hour(s) '
+ CAST(DATEPART(MINUTE, #MD) AS VARCHAR(2)) + ' minute(s) '
+ CAST(DATEPART(SECOND, #MD) AS VARCHAR(2)) + ' second(s)' as 'Median Time'
Output
0 day(s) 2 hour(s) 2 minute(s) 13 second(s)
I tried to use the CAST function so that I could run the queries once without running the two queries separately. I got errors.
SELECT TxnStartDT, TxnCompleteDT, TxnDuration,
PERCENTILE_CONT(.5) WITHIN GROUP (ORDER BY TxnDuration) OVER() AS MEDIAN
FROM(
SELECT DISTINCT TxnStartDT, TxnCompleteDT,
DATEDIFF(SECOND, TxnStartDT, TxnCompleteDT) AS TxnDuration
FROM MyTable
WHERE (TxnStartDT >='2023-01-02 00:00' and TxnStartDT <= '2023-01-08 23:59') and TxnCompleteDT is not null) AS D
DECLARE #MD DATETIME = CAST(DATEADD(SECOND, MEDIAN, 0))
SELECT --CAST(DATEPART(MONTH, #VARDT) - 1 AS VARCHAR(2)) + ' month(s) '
+ CAST(DATEPART(DAY, #MD) - 1 AS VARCHAR(2)) + ' day(s) '
+ CAST(DATEPART(HOUR, #MD) AS VARCHAR(2)) + ' hour(s) '
+ CAST(DATEPART(MINUTE, #MD) AS VARCHAR(2)) + ' minute(s) '
+ CAST(DATEPART(SECOND, #MD) AS VARCHAR(2)) + ' second(s)' as 'Median Time'
Errors
Msg 1035, Level 15, State 10, Line 32 Incorrect syntax near
'CAST', expected 'AS'. Msg 137, Level 15, State 2, Line 34
Must declare the scalar variable "#MD".

Answer 1

try this
;with cte as(SELECT TxnStartDT, TxnCompleteDT, TxnDuration,
cast (DATEADD(SECOND,PERCENTILE_CONT(.5) WITHIN GROUP (ORDER BY TxnDuration) OVER() ,0)as datetime) AS MEDIAN
FROM(
SELECT DISTINCT TxnStartDT, TxnCompleteDT,
DATEDIFF(SECOND, TxnStartDT, TxnCompleteDT) AS TxnDuration
FROM MyTable
WHERE (TxnStartDT >='2023-01-02 00:00' and TxnStartDT <= '2023-01-08 23:59') and TxnCompleteDT is not null) AS D)
SELECT
CAST(DATEPART(DAY, MEDIAN) - 1 AS VARCHAR(2)) + ' day(s) '
+ CAST(DATEPART(HOUR, MEDIAN) AS VARCHAR(2)) + ' hour(s) '
+ CAST(DATEPART(MINUTE, MEDIAN) AS VARCHAR(2)) + ' minute(s) '
+ CAST(DATEPART(SECOND, MEDIAN) AS VARCHAR(2)) + ' second(s)' as 'Median Time'
from cte