SQL: calculate column with dynamic pivot queries - sql

Question

I have a table in my database with all sensor measurements. The names of these sensors are stated in another table in the database. I would like to create a pivotted view with the datetime stamp of the measurements and the sensor names as colums. I would like to use some of these colums to calculate a new 'variable'.
The original table:
Id | DateTime | SensorId | Value
100 | 2019-01-01 00:00:00 | 1 | 19
101 | 2019-01-01 00:05:00 | 1 | 19
102 | 2019-01-01 00:10:00 | 1 | 19
109 | 2019-01-01 00:00:00 | 2 | 44,4
110 | 2019-01-01 00:05:00 | 2 | 44,3
111 | 2019-01-01 00:10:00 | 2 | 44,1
118 | 2019-01-01 00:00:00 | 3 | 338
119 | 2019-01-01 00:05:00 | 3 | 335
120 | 2019-01-01 00:10:00 | 3 | 330
I have two pieces of code, but I don't know how to 'merge' the parts that i need.
First I created a a simple pivotted table with:
DECLARE #cols AS NVARCHAR(MAX)='';
DECLARE #query AS NVARCHAR(MAX)='';
DECLARE #query2 AS NVARCHAR(MAX)='';
SELECT #cols = #cols + QUOTENAME([SensorId]) + ',' FROM (select distinct [SensorId] from [dbo].[Measurement] ) as tmp
select #cols = substring(#cols, 0, len(#cols)) --trim "," at end
set #query =
'SELECT [DateTime], [1] , [2], [3], [1] * [2] from
(
select [DateTime], [Value], [SensorId] from [dbo].[Measurement]
) src
pivot
(
max([Value]) for [SensorId] in (' + #cols + ')
) piv'
execute(#query)
This creates:
DateTime | 1 | 2 | 3 | Calculated column
2019-01-01 00:00:00 | 19 | 44,4 | 338 | 843,6
2019-01-01 00:05:00 | 19 | 44,3 | 335 | 841,7
2019-01-01 00:10:00 | 19 | 44,1 | 330 | 837,9
But in this table the columns are numbered (instead of named), and i need to know how many sensors I have.
I also managed to get a pivotted dynamic table with the names of the sensors, with this query:
DECLARE #columns NVARCHAR(MAX), #sql NVARCHAR(MAX);
SET #columns = N'';
SELECT #columns += N', p.' + QUOTENAME(Unicode)
FROM (SELECT distinct dbo.Unicode.Code as Unicode
FROM dbo.Measurement INNER JOIN
dbo.Sensor ON Sensor.Id = Measurement.SensorId INNER JOIN
dbo.SensorModel on SensorModel.Id = Sensor.Id INNER JOIN
dbo.Unicode on Unicode.Id = SensorModel.UnicodeId) AS x;
SET #sql = N'
SELECT ' + STUFF(#columns, 1, 2, '') + '
FROM
(
Select dbo.Measurement.DateTime, dbo.Unicode.Code as Unicode, dbo.Measurement.Value as value
FROM dbo.Measurement INNER JOIN
dbo.Sensor ON Sensor.Id = Measurement.SensorId INNER JOIN
dbo.SensorModel on SensorModel.Id = Sensor.Id INNER JOIN
dbo.Unicode on Unicode.Id = SensorModel.UnicodeId
) AS j
PIVOT
(
max(value) FOR Unicode IN ('
+ STUFF(REPLACE(#columns, ', p.[', ',['), 1, 1, '')
+ ')
) AS p;';
PRINT #sql;
EXEC sp_executesql #sql;
Result:
Temperature1 | Temperature2
44,4 | 338
44,3 | 335
44,1 | 330
However I dont know how to add the Datetime and calculate an extra variable. I know which sensornames I would like to multiply. So i figured it would be something like ... SELECT [DateTime], ' + STUFF(#columns, 1, 2, '') + ' [Temperature1]*[Temperature2] FROM ... but this, ofcourse, doesn't do the trick.
To be clear, I woul like to have this table:
DateTime | Temperature1 | Temperature2 | Calculated column
2019-01-01 00:00:00 | 19 | 44,4 | 843,6
2019-01-01 00:05:00 | 19 | 44,3 | 841,7
2019-01-01 00:10:00 | 19 | 44,1 | 837,9