PowerQuery PowerBI merge 2 tables based on condition between StartDate and EndDate - powerbi

Question

I try to join 2 tables using Power Query/PowerBI: Absence and dimDate to create a result table below:
Absence table
+------------+--------------+--------------+-----------+-----------+
| EmployeeId | EmployeeName | AbsenceType | StartDate | EndDate |
+------------+--------------+--------------+-----------+-----------+
| 1 | A | Annual Leave | 2/01/2017 | 5/01/2017 |
| 2 | B | Sick Leave | 4/01/2017 | 6/01/2017 |
+------------+--------------+--------------+-----------+-----------+
dimDate table
+------------+
| FullDate |
+------------+
| 1/01/2017 |
| 2/01/2017 |
| 3/01/2017 |
| 4/01/2017 |
| 5/01/2017 |
| 6/01/2017 |
| 7/01/2017 |
| 8/01/2017 |
| 9/01/2017 |
| 10/01/2017 |
+------------+
Result
+------------+--------------+--------------+-----------+
| EmployeeId | EmployeeName | AbsenceType | Date |
+------------+--------------+--------------+-----------+
| 1 | A | Annual Leave | 2/01/2017 |
| 1 | A | Annual Leave | 3/01/2017 |
| 1 | A | Annual Leave | 4/01/2017 |
| 1 | A | Annual Leave | 5/01/2017 |
| 2 | B | Sick Leave | 4/01/2017 |
| 2 | B | Sick Leave | 5/01/2017 |
| 2 | B | Sick Leave | 6/01/2017 |
+------------+--------------+--------------+-----------+
I usually use SQL to create this result, however I don't know how to efficiently do it in PowerQuery.
SELECT A.EmployeeId
,A.EmployeeName
,A.AbsenceType
,D.FullDate
FROM Absence AS A
INNER JOIN dimDate AS D ON (
D.FullDate >= A.StartDate
AND D.FullDate <= A.EndDate
)
Note: I have tried the Full Join between 2 tables Absence and dimDate, then filter true value if dimDate.FullDate >= StartDate and dimDate.FullDate <= EndDate. However this approach seems to be ineffective with large table, and it creates redundant records before filtering so it's quite slow.
Please give me some advice.

Answer 1

No need to merge. You can create a column with embedded lists of all dates between StartDate and EndDate. And then expand that column.
let
Source = Table1,
#"Added Custom" = Table.AddColumn(Source, "Date", each List.Dates([StartDate],1+Duration.Days([EndDate]-[StartDate]),#duration(1,0,0,0))),
#"Expanded Date" = Table.ExpandListColumn(#"Added Custom", "Date"),
#"Changed Type" = Table.TransformColumnTypes(#"Expanded Date",{{"Date", type date}}),
#"Removed Columns" = Table.RemoveColumns(#"Changed Type",{"StartDate", "EndDate"})
in
#"Removed Columns"