Sql Server: Get count of * or distinct rows for column A grouped by column B

Scenario 1 - count of * rows:

A table has 10 records. Column B has duplicate rows with different values in Column A

then., Sql Query:

Code Snippet:

SELECT COUNT(ColumnA) AS Count_Headertext,

ColumnB AS ColumnB_Headertext

FROM Tablename

GROUP BY ColumnB

Scenario 2 - count of distinct rows:

A table has 10 records. Column B has duplicate rows with different values in Column A

then., Sql Query:

Code Snippet:

SELECT COUNT(DISTINCT ColumnA) AS Count_Headertext,

ColumnB AS ColumnB_Headertext

FROM Tablename

GROUP BY ColumnB