How to Join in TSQL

CREATE TABLE dbo.Tab1 (Col1 VARCHAR(10), Col2 VARCHAR(10))
CREATE TABLE dbo.Tab2 (Col1 VARCHAR(10), Col2 VARCHAR(10))
 
INSERT INTO dbo.Tab1 (Col1, Col2)
SELECT 'Row1','A'
UNION ALL 
SELECT 'Row2','A'
UNION ALL 
SELECT 'Row3','A'
UNION ALL 
SELECT 'Row4','A'
UNION ALL 
SELECT 'Row5','A'
UNION ALL 
SELECT 'Row6','A'
 
INSERT INTO  dbo.Tab2 (Col1, Col2)
SELECT 'Row1','B'
UNION ALL 
SELECT 'Row2','B'
UNION ALL 
SELECT 'Row3','B'
 

SELECT T2.Col1,T2.Col2  
FROM dbo.Tab2 T2 
UNION
SELECT T1.Col1 , T1.Col2
FROM dbo.Tab1 T1 
WHERE T1.Col1 IN (SELECT Col1 FROM dbo.Tab2)