Query to return multiple rows based on the value in a column - powerbi

Question

I have a source table that has projects with a start date and duration in months. I'm looking to write a PowerQuery for PowerBI that will create a row for each month of the project, counting up the months. For example:
Source:
Project(string) | Date (ms timestamp) | Duration (integer)
A | Jan-2022 | 3
B | Sep-2022 | 2
Result:
Project | Date
A | Jan-2022
A | Feb-2022
A | Mar-2022
B | Sep-2022
B | Oct-2022
Not sure where to start or what this query should look like. Any ideas?
Edit: Changed sample tables to make them readable
Edit: Dates in the source table are provided in millisecond timestamp format (eg 1641024000000). My intent in the result table is to have them in a human-readable date format.

Answer 1

Here is one way to do this in Power Query.
Paste the code into a blank query.
Then Change the Source line so as to load your actual data table.
I used an Excel table for the source, but you may use what ever.
I also have the unix time stamp in the Source table, converting it to a PQ date in the M Code.
If all of your time stamps do not equate to the start of the month, some additional logic may be required.
Read the code comments and explore the Applied Steps to understand the algorithm
let
//Read in the Source data
Source = Excel.CurrentWorkbook(){[Name="Table27"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Project", type text}, {" Date", Int64.Type}, {" Duration", Int64.Type}}),
//convert date from unixTime in milliseconds to a PQ date
unixTime = Table.TransformColumns(#"Changed Type",{" Date", each #duration(0,0,0,_/1000)+#date(1970,1,1)}),
//add custom column with a List of the desired dates
#"Added Custom" = Table.AddColumn(unixTime, "Months", each
List.Accumulate(
{0..[#" Duration"]-1},
{},
(state,current)=> state & {Date.AddMonths([#" Date"],current)})),
//Remove unneeded columns
//Expand the list and set the data thype
#"Removed Columns" = Table.RemoveColumns(#"Added Custom",{" Date", " Duration"}),
#"Expanded Months" = Table.ExpandListColumn(#"Removed Columns", "Months"),
#"Changed Type1" = Table.TransformColumnTypes(#"Expanded Months",{{"Months", type date}})
in
#"Changed Type1"

Answer 2

For some reason sqlfiddle was down for me so I made an example in db-fiddle using postgres instead of ms-sql.
What you're looking to accomplish can be done with a recursive CTE, the syntax in MS-SQL is slightly different but this should get you most of the way there.
WITH RECURSIVE project_dates AS(
SELECT
start_date as starting_date,
CAST(start_date + duration*INTERVAL '1 month' as date) as end_date,
project
FROM projects
UNION
SELECT
CAST(starting_date + INTERVAL '1 month' as date),
pd.end_date,
p.project
FROM projects p
JOIN project_dates pd ON pd.project = p.project
WHERE CAST(starting_date + INTERVAL '1 month' as date) < pd.end_date
)
SELECT starting_date, project FROM project_dates
ORDER BY project, starting_date
My results using your date look as such.
You can check out my answer on db-fiddle with this link: https://www.db-fiddle.com/f/iS7uWFGwiMbEmFtNmhsiWt/0

Answer 3

try below
Divide your milliseconds by 86400000 and add that to 1/1/1970 to get date
Create an array based on Duration, expand to rows, add that to the start date
Remove extra columns
let Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
ConvertToDays = Table.TransformColumns(Source,{{"Date", each Number.RoundDown(Number.From(_) / 86400000)}}),
#"Added Custom" = Table.AddColumn(ConvertToDays, "Custom", each Date.AddDays(#date(1970,1,1),18993)),
#"Added Custom1" = Table.AddColumn(#"Added Custom", "Custom.1", each List.Numbers(0,[Duration])),
#"Expanded Custom.1" = Table.ExpandListColumn(#"Added Custom1", "Custom.1"),
#"Added Custom2" = Table.AddColumn(#"Expanded Custom.1", "Custom.2", each Date.AddMonths([Custom],[Custom.1]), type date),
#"Removed Columns" = Table.RemoveColumns(#"Added Custom2",{"Date", "Duration", "Custom", "Custom.1"}),
#"Renamed Columns" = Table.RenameColumns(#"Removed Columns",{{"Custom.2", "Date"}}),
TextDate = Table.AddColumn(#"Renamed Columns", "TextDate", each Date.ToText([Date],"MMM-yy"))
in TextDate