我如何在同一时间连接到两个数据库并在mysql中查询数据

Question

I have two Database, A & B how I can copy data from A to B using MySQL, i did like there something wrong, there are two same tables called members in A & B, and i want copy username from A.members to B.members. there is error ! can I do that using Mysql, anyone can help me to solve this problem because I must connect to databases A & B in same time then query data

    mysql_connect("$host", "$user", "$pass"); mysql_select_db("A");
    mysql_connect("$host", "$user2", "$pass2"); mysql_select_db("B"); 
   //host A = host B same host 
    $MySQL="Select username FROM A.members INSERT INTO B.members"; 
    $result= mysql_query($MySQL);

Answer 1

If you are connecting to the same host, you only need to make the connection once. And setting the default database using mysql_select_db("A"); should not be necessary because you are specifying which database to use in your statement.

The SQL for your insert should be:

INSERT INTO B.members (username) SELECT username FROM A.members

Check out the documentation for INSERT...SELECT .

Answer 2

create two connection and use it in query eg:

  $con = mysqli_connect("localhost","root","","db1");
        $con2 = mysqli_connect("localhost","root","","db2");
         $query1 = mysqli_query($con1,"SELECT * FROM tbl1 order by ID desc ");
         while($row = $query1 ->fetch_assoc())
      {

         $query2 = mysqli_query($con2,"insert into  tbl2 (fields) values('".$row['field
']."')");

}