Excel merge two tables, repeating 2nd table lookup row - excel

Question

I have two Excel Tables with a 'lookup' column to merge against. I want to merge to a new table with all the lookup values expanded. If I were doing this in python or some such, the pseudo-code would be something like:
for unique day in Tbl1
row1 = day
row2 = ""
for event in Tbl1 day
v = event's lookup value in Tbl2
row1 += event + (len(v) - 1) blank columns
row2 += v
print(row1)
print(row2)
I'd like to avoid VBA, but would like to use new dynamic array functions (preferred) or power query (if necessary), but I can't figure out how to get the repeat to happen. The power query merges I've tried aren't complete.
The original data (where I've used abbreviations for my real data), has a number of events per day. The 'lookup' column shows the different levels of that event for that day.
Tbl1
day
event
lookup
1
Re
eoni2
1
Gr
eoni1
1
We
eoni1
2
Tn
eoneonii2
2
Ga
eon1
2
Gr
eoni1
Tbl2
lookup
c1
c2
c3
c4
c5
c6
c7
c8
eeononii
E
E
O
N
O
N
I
I
eon1
E
O
N
eoneonii2
E
O
N
E
O
N
I
I
eoni1
E
O
N
I
eoni2
E
E
O
O
N
N
I
I
Tbl1
Data will change: number of events per day, event value, what lookup value might be for an event.
The 'event' may or may not repeat from one day to the next, but will be unique within a day.
Order (top to bottom) should be maintained in resulting merge (left to right).
Max number of days = 3.
Tbl2
generally static and top to bottom order can be changed if needed.
may contain entries that are not used by Tbl1.
min of 3 and max of 8 values per row.
Tbl3 output
ideally, the 'event' name would not repeat, as shown below, but can if it keeps formula cleaner.
the number of columns for each day in output Tbl3 may not be the same, as shown, e.g. day 1 rows have 16 and day 2 rows have 15 here.
The output I want:
Tbl3
day
e1
e2
e3
e4
e5
e6
e7
e8
e9
e10
e11
e12
e13
e14
e15
e16
1
Re
Gr
We
E
E
O
O
N
N
I
I
E
O
N
I
E
O
N
I
2
Tn
Ga
Gr
E
O
N
E
O
N
I
I
E
O
N
E
O
N
I
Thanks much.

Answer 1

This can be accomplished using Power Query, available in Windows Excel 2010+ and Excel 365 (Windows or Mac)
To use Power Query
Select some cell in your Data Table
Data => Get&Transform => from Table/Range or from within sheet
When the PQ Editor opens: Home => Advanced Editor
Make note of the Table Name in Line 2
Paste the M Code below in place of what you see
Change the Table name in line 2 back to what was generated originally.
Read the comments and explore the Applied Steps to understand the algorithm
M Code
let
//Read in both tables
//Edit Source and Source1 lines to reflect your actual table names
Source = Excel.CurrentWorkbook(){[Name="Tbl_1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"day", Int64.Type}, {"event", type text}, {"lookup", type text}}),
Source1 = Excel.CurrentWorkbook(){[Name="Tbl_2"]}[Content],
#"Changed Type1" = Table.TransformColumnTypes(Source1,
List.Transform(Table.ColumnNames(Source1), each {_, type text})),
//Join the two tables based on the lookup column
//then remove that column
#"Join Tables" = Table.NestedJoin(#"Changed Type","lookup", #"Changed Type1","lookup", "joined"),
#"Removed Columns" = Table.RemoveColumns(#"Join Tables",{"lookup"}),
//Add index column to maintain original Event order
#"Added Index" = Table.AddIndexColumn(#"Removed Columns", "Index", 0, 1, Int64.Type),
//Expand the joined table and remove the Index column
#"Expanded joined" = Table.ExpandTableColumn(#"Added Index", "joined", {"c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8"}, {"c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8"}),
#"Removed Columns2" = Table.RemoveColumns(#"Expanded joined",{"Index"}),
//Unpivot all the "value" columns
//Then remove the "Attribute" column (the previous column Headers)
#"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Removed Columns2", {"day", "event"}, "Attribute", "Value"),
#"Removed Columns1" = Table.RemoveColumns(#"Unpivoted Other Columns",{"Attribute"}),
//Group by "day"
#"Grouped Rows" = Table.Group(#"Removed Columns1", {"day"}, {
{"event & value", (t)=> let
remDay = Table.RemoveColumns(t,"day"),
//replace all except first event of a type with null
nullEvents = List.Accumulate(t[event],{}, (state,current)=>
if state = {} then {current}
else if List.Contains(state,current) then state & {null}
else state & {current}),
//then create new table and Transpose to get final format
newTable = Table.Transpose(Table.FromColumns(
{nullEvents, t[Value]}
))
in
newTable}
}),
//Calculate number of columns for creating column names
numCols = List.Max(List.Transform(#"Grouped Rows"[#"event & value"], each Table.ColumnCount(_))),
//expand the grouped columns and set the appropriate names
#"Expanded event & value" = Table.ExpandTableColumn(#"Grouped Rows", "event & value",
List.Transform(List.Numbers(1,numCols), each "Column" & Text.From(_)),
List.Transform(List.Numbers(1,numCols), each "e" & Text.From(_))),
//Replace alternate "day" with null
replaceWithNulls = Table.FromColumns(
{List.Accumulate(#"Expanded event & value"[day], {}, (state,current)=>
if Number.IsOdd(List.Count(state))
then state & {null} else state & {current})} &
Table.ToColumns(Table.RemoveColumns(#"Expanded event & value","day")),
Table.ColumnNames(#"Expanded event & value")
),
//set the data types
typeit = Table.TransformColumnTypes(replaceWithNulls,
{{"day", Int64.Type}} & List.Transform(List.RemoveFirstN(Table.ColumnNames(replaceWithNulls),1), each {_, type text}))
in
typeit