How to count values of columns???

Hello huynq 

this involves some unpivoting, grouping and pivoting. Check out this code example

let
	Source = #table 
	(
		{ "A", "B", "C", "D" },
		{ { "a", "b", "c", "d" }, { "a", "b", "a", "a" }, { "c", "a", "d", "o" } } 
	),
	Unpivot = Table.UnpivotOtherColumns 
	(
		Source,
		{ },
		"Attribute",
		"Value" 
	),
	Group = Table.Group 
	(
		Unpivot,
		{ "Attribute", "Value" },
		{ { "Count", each Table.RowCount ( _ ), type number } } 
	),
	Pivot = Table.Pivot 
	(
		Group,
		List.Distinct 
		(
			Group [ Attribute ] 
		),
		"Attribute",
		"Count",
		List.Sum 
	)
 in 
	Pivot

Copy paste this code to the advanced editor in a new blank query to see how the solution works. If this solution fits your need, copy and past a part of it and implement it in your query, or I could create a custom function what makes it easier to apply if you are not used that much to power query.

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy

Hello huynq 

just use this code instead

let
	Source = #table 
	(
		{ "A", "B", "C", "D" },
		{ { "a", "b", "c", "d" }, { "a", "b", "a", "a" }, { "c", "a", "d", "o" } } 
	),
	Unpivot = Table.UnpivotOtherColumns 
	(
		Source,
		{ },
		"Attribute",
		"Value" 
	),
	Group = Table.Group 
	(
		Unpivot,
		{ "Attribute", "Value" },
		{ { "Count", each Table.RowCount ( _ ), type number } } 
	),
	Pivot = Table.Pivot 
	(
		Group,
		List.Distinct 
		(
			Group [ Attribute ] 
		),
		"Attribute",
		"Count",
		each if List.IsEmpty(_) then 0 else List.Sum (_)
	)
 in 
	Pivot

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy