Syntax for adding values in one column of attribute table based on value in another column ArcGIS Pro

Question

I have several shapefile layers with census tract data in ArcGIS Pro. There are two types, layer A, with only the tract number - therefore statistics (count, percentage, etc) are based on the entire tract, and layer B, with tract number AND block group, meaning statistics in layer B are further broken down.

I need to join the two layers based on tract (which I can do), but I am unsure how to add the values in the percentage column of layer B based on their common tract.

another example to illustrate, Layer A

Tract #	Qualifying Pct
8825	50%
8824	10%

while Layer B looks like

Tract #	Block Group	Qualifying Pct
8825	1	25%
8825	2	25%
8824	4	7%
8824	1	3%

Ultimately, I want one layer, with one percent value per tract.

Answer 1

As you have only 1 row per track number in layer A you need to match that 1-to-1 with layer B. To achieve that, use the pivot table tool to restructure your table B, then do your join on tract number.

Pivot it into

tract #, BG1, BG2, BG3, BG4
8825, 25,25,null,null
8824,3,null,null,7