How do i compare two tables to get desired result in SQL Server

The stored procedure like below.

SQL

CREATE PROC GetMessage
    @UserName VARCHAR(20)
AS
BEGIN
    SELECT u.Name,u.ImageName,u.UserName,up.UserName,up.FriendUserName,up.MESSAGE,up.ContentPost,up.ImageName1,up.SendDate 
    FROM USERPost up
    JOIN User3 u ON u.UserName = up.USERNAME
    WHERE up.USERNAME IN(
                        SELECT uf.UserName FROM USERFollow uf
                        WHERE (uf.UserName = @UserName OR uf.FriendUserName = @UserName) AND uf.FollowStatus = 'true'
                        UNION
                        SELECT uf.FriendUserName FROM USERFollow uf
                        WHERE (uf.UserName = @UserName OR uf.FriendUserName = @UserName) AND uf.FollowStatus = 'true'
                        )
    ORDER BY up.SendDate DESC
END