This blog defines the method of merging the data of two tables, in SQL Server.
CREATE TABLE #tbl_1 (sno INT IDENTITY(1,1),name NVARCHAR(100),id INT)
CREATE TABLE #tbl_2 (sno INT IDENTITY(1,1),name NVARCHAR(100),id INT)
INSERT INTO #tbl_1 VALUES ('kiran','9876')
INSERT INTO #tbl_1 VALUES ('praveen','7654')
INSERT INTO #tbl_2 VALUES ('raju','245')
INSERT INTO #tbl_2 VALUES ('vamshi','386')
SELECT ROW_NUMBER() OVER(ORDER BY id DESC) AS sno,*
FROM (
SELECT name,id FROM #tbl_1
UNION ALL
SELECT name,id FROM #tbl_2
) temp
DROP TABLE #tbl_1
DROP TABLE #tbl_2