Merge queries matching on dates and leave null if no match found - merge

Question

I have got two tables below (examples):
Table SFID
Sales Force ID
Type
Name
Assistant
From
To
123
ABC
Store A
Ben
01/04/2020
30/04/2020
123
ABC
Store A
Jen
01/05/2020
31/05/2020
123
ABC
Store A
Ben
01/06/2020
21/06/2020
126
DEF
Store B
Tim
01/04/2020
30/04/2020
126
DEF
Store B
Tim
01/04/2020
null
and
Table Activity
Transaction ID
Date
Sales Force ID
1
03/05/2020
123
2
03/06/2020
200
3
01/01/2021
123
4
02/01/2021
126
I want my end result to be
Transaction ID
Date
Sales Force ID
Type
Name
Assistant
1
03/05/2020
123
ABC
Store A
Jen
2
03/06/2020
200
null
null
null
3
01/01/2021
123
null
null
null
4
02/01/2021
126
DEF
Store B
Tim
To do this, the best solution was the one posted in here with some modifications (allow both To and From to be null). However, only the row on transaction ID 2 disappears because that Sales Force had already had assistant entries (they get wiped out on the filtered row step). I also tried the solution presented in here but it takes ages to load.
I would like to know if there was a way to guarantee all transactions appear without having to introduce lines to table SFID for periods they don't have assistants and without making the query a really slow one.
This is my code:
let
Source = Source,
#"Merged Queries" = Table.NestedJoin(Source,{"Sales Force ID"},SFID,{"SFID"},"SFID",JoinKind.LeftOuter),
#"Expanded SFID" = Table.ExpandTableColumn(#"Merged Queries", "SFID", {"Type", "Name", "Assistant", "From", "To"}, {"Type", "Name", "Assistant", "From", "To"}),
#"Changed Type" = Table.TransformColumnTypes(#"SFID",{{"Date", type date}, {"From", type date}, {"To", type date}}),
FilteredRows = Table.SelectRows(#"Changed Type", each ([Date] >= [From] and [Date] <= [To]) or ([Date] >= [From] and [To] = null)or ([From] = null and [To] = null)),
#"Removed Columns" = Table.RemoveColumns(FilteredRows,{"From", "To"})
in
#"Removed Columns"

Answer 1

So after almost 2 weeks with no response and an unjustified downgrade, I found a solution!
I created a query that would basically produce this table with the above mentioned code.
Transaction ID
Date
Assistant
1
01/01/2021
Jen
4
02/01/2021
Tim
let
Source = Source,
#"Merged Queries" = Table.NestedJoin(Source,{"Sales Force ID"},SFID,{"SFID"},"SFID",JoinKind.LeftOuter),
#"Expanded SFID" = Table.ExpandTableColumn(#"Merged Queries", "SFID", {"Type", "Name", "Assistant", "From", "To"}, {"Type", "Name", "Assistant", "From", "To"}),
#"Changed Type" = Table.TransformColumnTypes(#"Expanded SFID",{{"Date", type date}, {"From", type date}, {"To", type date}}),
FilteredRows = Table.SelectRows(#"Changed Type", each ([Date] >= [From] and [Date] <= [To]) or ([Date] >= [From] and [To] = null)),
#"Removed Columns" = Table.RemoveColumns(FilteredRows,{"From", "To"})
in
#"Removed Columns"
And left-joined it on my initial version of Table Activity
I kept the information of type Type and Name in a separate Query (as they don't change) and then again left-joined it on the Table Activity.
Final query looks like this:
let
Source = Source,
#"Merged Queries1" = Table.NestedJoin(Source,{"Sales Force Code"},Info,{"SFID"},"Info",JoinKind.LeftOuter),
#"Expanded Info" = Table.ExpandTableColumn(#"Merged Queries1", "Info", {"Type", "Name"}, {"Type", "Name"}),
#"Merged Queries" = Table.NestedJoin(#"Expanded Info",{"ID"},IDvsAssistant,{"ID"},"IDvsAssistant",JoinKind.LeftOuter),
#"Expanded IDvsAssistant" = Table.ExpandTableColumn(#"Merged Queries", "IDvsAssistant", {"Assistant"}, {"Assistant"})
in
#"Expanded IDvsAssistant"