In response to my post showing how to union two tables in Excel  a reader writes,

I have seen your blog post about combining two tables, which I have working for me, however I would like to combine an ever increasing number of tables …, into a common “list”. How to do it without ending up with a nest IF statement beyond all control?!

We can avoid writing a deeply nested IF statement by creating a table that does some of the work for us.

The logic of the solution is the same as for the two table problem. A cell in the output table must ask,

  • “Which table should I get my value from?” and
  • “Which row should I get my value from?”

We create a helper table with this information in it.

First, let’s look at the work book, this has three tables to union, a helper table and an output table.

union workbook

Below we see the “Tables to union” table,

tables to union

The table columns are

  • Table Name: The names of the table in the union
  • Table Rows: The number of rows in this table
    • =ROWS(INDIRECT([@[Table Name]]))
  • Start Row In Union Table:
    • =SUM(OFFSET([Table Rows],-1,0,ROW()-ROW(Tables_To_Union[[#Headers],[Start Row In Union Table]])))+1
    • This bizarre formula simply make a running total in Table Rows and adds 1.

union table

Each row in the union table can now simply lookup its value

  • RowId =ROW(Table_union[@])-ROW(Table_union[[#Headers],[RowId]])
  • Which Table =VLOOKUP([@RowId],Tables_To_Union,3,TRUE)
  • Which Row =[@RowId]-VLOOKUP([@RowId],Tables_To_Union,1,TRUE)+1
  • Column1 = =IFERROR(INDEX(INDIRECT([@[Which Table]]),[@[Which Row]],COLUMN()-COLUMN(Table_union[@])-2),”no more records”)
  • Column2 =IFERROR(INDEX(INDIRECT([@[Which Table]]),[@[Which Row]],COLUMN()-COLUMN(Table_union[@])-2),”no more records”)

I think that this solution is quite elegant because it is easy to add additional tables and columns to the union and is reasonably readable. However when time allows I might write a custom function in VBA that uses the same logic.

I hope that you find this useful.

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