PHP based connection Mysql database and query data _mysql

Three ways to connect to a database

1. General mode:

$con =mysql_connect ($dbhostip, $username, $userpassword) or die ("Unable to connect to the mysql!");
$db = mysql_select_db ($dbdatabasename, $con);
Executes
the statement $qres =mysql_query ("SELECT id,goodsname from User");
Extract a data one
$row =mysql_fetch_row ($result);//mysql_fetch_row can only extract the first record of the query result
//Extract multiple records
$reslist = Array ( );
$i =0;
while ($row = Mysql_fetch_row ($res)) {
   $reslist [$i] = $row;
   $i + +;
  }
Mysql_close ($con);

The result of mysql_fetch_row extraction is that there are no field names in the query (that is, no key id,goodsname, only values), as shown in the following figure:

The result of MYSQL_FETCH_ASSOC extraction has a key value, as shown in the following figure:

The result of mysql_fetch_array extraction is a key value, which is the first two kinds of synthesis, the following figure:

Using the @ (Error control operator) before mysql_connect (), mysql_select_db (), and so on, you can ignore the error message from the system, and then we use Die () to customize the error message;

For the return value of the mysql_query () function, if the executed statement has return values (such as SELECT, Show, describe, and so on), the corresponding data is returned (when it succeeds) or false (when it fails), if the executed statement does not have a return value (such as Delete, DROP, INSERT, update, and so on), returns True (when it succeeds) or false (when it fails).

2. Object-Oriented form

$db =new mysqli ($dbhostip, $username, $userpassword, $dbdatabasename);

if (Mysqli_connect_error ()) {  

echo ' could not connect to database. '  

Exit;

}

$result = $db->query ("Select Id,goodsname from User");

$row = $result->fetch_row ();

Here's the mysqli, which means MySQL is extended to interact with the database either through a process-oriented approach or through an object-oriented approach.

3. Pdo method

PDO is actually the abbreviation of PHP database objects, the Chinese is the PHP object. It provides a unified way for PHP to interact with the database.

Its advantage is that as long as the data source is provided correctly, the rest of the basic operation of the database is the same. That is, the same piece of code can interact with MySQL, interact with SQLite3, and, of course, interact with PostgreSQL, provided you provide the right data source.

Code to connect to MySQL:

$dsn = ' mysql:host= '. $dbhost '; Dbname= '. $dbdatabase. ' $dbh =new PDO ($dsn, $username, $userpass);

SQLite3:

$dsn = ' sqlite3: ' D:\sqlite\user.db ';
$DBH =new PDO ($DSN);

PostgreSQL:
$dsn = ' pgsql:host= '. $dbhost. ' port=5432 dbname= '. $dbdatabase. ' user= '. $ $username. $ Userpass;
$DBH =new PDO ($DSN);

Operation:

$stmt = $dbh->query (' SELECT id,name from user ');
$row = $stmt->fetch ();