Take a SQL Server object (view, table), grab its columns, count distinct its values, and return them in descending order of cardinality

data_sampler.sql

CREATE OR ALTER procedure #data_sampler
(
	@schema_name NVARCHAR(128) = 'dbo',
	@object_name NVARCHAR(128)
)
AS 
BEGIN	
	SET NOCOUNT ON;

	DECLARE 
		@SQL NVARCHAR(MAX) = 
		'
SELECT *
FROM 
( 
	SELECT 	
		/*column_list_with_distinct*/		
	FROM ' + QUOTENAME(@schema_name) + '.' + QUOTENAME(@object_name)+' AS t
) AS summary
UNPIVOT
(
	row_count 
	FOR 
	table_name IN 
	(
		/*column_list*/
	)
) AS unp
ORDER BY 
	row_count DESC 
		',
		@column_list_with_distinct NVARCHAR(MAX),
		@column_list NVARCHAR(MAX),
		@magic_value NVARCHAR(73) = '39EACB36-3C89-4E6B-A488-15F8F7E5D363-9CC5643D-8F87-422D-BA48-34A28029CE7B'

	SELECT 						
		@column_list_with_distinct = 
			STRING_AGG
			(
				CONVERT
				(
					NVARCHAR(MAX),
					CONCAT
					(
						'COUNT(DISTINCT CASE WHEN ',
						QUOTENAME(c.name),
						' IS NULL THEN @magic_value ELSE CONVERT(VARCHAR(MAX),',
						QUOTENAME(c.name),
						') END ) AS ',
						QUOTENAME(c.name)
					)
				),
				CONCAT
				(
					',',
					CHAR(10),
					CHAR(9),
					CHAR(9) 
				)
			),
		@column_list = 
			STRING_AGG(QUOTENAME(c.name), ',')
	FROM sys.objects AS so
	JOIN sys.schemas AS s ON 
		s.schema_id = so.schema_id
	JOIN sys.columns AS c ON
		so.object_id = c.object_id
	WHERE
		so.name = @object_name
		AND s.name = @schema_name
	END 

	SET @SQL = REPLACE(REPLACE(@SQL,'/*column_list_with_distinct*/',@column_list_with_distinct),'/*column_list*/',@column_list)	
	EXEC sp_executesql @SQL, N'@magic_value NVARCHAR(73)', @magic_value = @magic_value
GO