Concatenate vlookup results

[jdgel817]

How do I accomplish this with a formula? I need the vlookup results to be concatenated into a single cell. Thanks.

Initial Table		Lookup Results
Class	Name		Class	Name
Class1	Bob		Class1	Bob, Lily, Alice
Class2	Jane		Class2	Jane, David, Sara
Class3	John		Class3	John, Lucy
Class2	David		Class4	Sally, James
Class4	Sally
Class1	Lily
Class1	Alice
Class2	Sara
Class4	James
Class3	Lucy

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[DRSteele]

You will need Excel2016 for this formula to work with the new function TEXTJOIN.

Book1
	A	B	C	D	E
1	Initial Table			Lookup Results
2	Class	Name		Class	Name
3	Class1	Bob		Class1	Bob, Lily, Alice
4	Class2	Jane		Class2	Jane, David, Sara
5	Class3	John		Class3	John, Lucy
6	Class2	David		Class4	Sally, James
7	Class4	Sally
8	Class1	Lily
9	Class1	Alice
10	Class2	Sara
11	Class4	James
12	Class3	Lucy
Sheet57

Cell Formulas
Range	Formula
E3	{=TEXTJOIN(", ",,IF($A$3:$A$12=D3,$B$3:$B$12,""))}
Press CTRL+SHIFT+ENTER to enter array formulas.