Database

-- Join in WHERE clause.
USE pubs
SELECT t.title_id, t.title, s.qty
FROM titles AS t, sales AS s
WHERE t.title_id *= s.title_id

-- Join in FROM clause.
USE pubs
SELECT t.title_id, t.title, s.qty
FROM titles AS t LEFT OUTER JOIN sales AS s
   ON t.title_id = s.title_id

-- Join and search condition in WHERE clause.
USE pubs
SELECT t.title_id, t.title, s.qty
FROM titles AS t, sales AS s
WHERE t.title_id *= s.title_id
   AND s.stor_id = '7066'

USE pubs
SELECT t.title_id, t.title, s.qty
FROM titles AS t LEFT OUTER JOIN sales AS s
   ON t.title_id = s.title_id
WHERE s.stor_id = '7066'

USE pubs
SELECT t.title_id, t.title, s.qty
FROM titles AS t LEFT OUTER JOIN sales AS s
   ON t.title_id = s.title_id 
   AND s.stor_id = '7066'

string strTarget = @"C:\books\";
string connection = "server=(local);database=books;trusted_connection=true;";
 
using(SqlConnection cn = new SqlConnection(connection))
{
    cn.Open();
    
    using(SqlCommand cmd = new SqlCommand("SELECT [Name] FROM Books", cn))
    using(SqlDataReader rst = cmd.ExecuteReader(CommandBehavior.CloseConnection))
    {
        while(rst.Read())
        {
            DirectoryInfo book = new DirectoryInfo(
                Path.Combine(strTarget, rst.GetString(0));
            
            if (!book.Exists)
                book.Create();
        }
        rst.Close();
    }
    
    cn.Close();
}