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    mysql_select_db

    (PHP 4, PHP 5)

    mysql_select_db — MySQL 데이터베이스를 선택

    설명

    bool mysql_select_db ( string $database_name [, resource $link_identifier ] )

    접속 지시자와 연관된 서버에서 현재 활성화할 데이터베이스를 선택한다. 모든 수반되는 mysql_query() 호출은 활성 데이터베이스에서 처리될 것이다.

    인수

    database_name

    선택할 데이터베이스의 이름.

    link_identifier

    MySQL 연결. 지정하지 않으면 mysql_connect()로 연 마지막 연결을 사용합니다. 연결이 없으면, 인수 없이 mysql_connect()를 호출하여 연결을 만듭니다. 연결이 성립되지 않으면 E_WARNING 등급의 오류를 생성합니다.

    반환값

    성공 시 TRUE를, 실패 시 FALSE를 반환합니다.

    예제

    Example #1 mysql_select_db() 예제

    <?php

    $link     = mysql_connect('localhost', 'mysql_user', 'mysql_password');
    if (!    $link) {
        die(    'Not connected : ' . mysql_error());
    }

    // make foo the current db
    $db_selected = mysql_select_db('foo', $link);
    if (!    $db_selected) {
        die (    'Can\'t use foo : ' . mysql_error());
    }
    ?>

    주의

    Note:

    하위 호환을 위하여, 다음의 권장하지 않는 별칭을 사용할 수 있습니다: mysql_selectdb()

    참고

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    User Contributed Notes 8 notes

    up
    15
    james at gogo dot co dot nz
    20 years ago
    Be carefull if you are using two databases on the same server at the same time.  By default mysql_connect returns the same connection ID for multiple calls with the same server parameters, which means if you do

    <?php
      $db1     = mysql_connect(...stuff...);
          $db2 = mysql_connect(...stuff...);
          mysql_select_db('db1', $db1);
          mysql_select_db('db2', $db2);
    ?>

    then $db1 will actually have selected the database 'db2', because the second call to mysql_connect just returned the already opened connection ID !

    You have two options here, eiher you have to call mysql_select_db before each query you do, or if you're using php4.2+ there is a parameter to mysql_connect to force the creation of a new link.
    up
    1
    Maarten
    18 years ago
    About opening connections if the same parameters to mysql_connect() are used: this can be avoided by using the 'new_link' parameter to that function.

    This parameter has been available since PHP 4.2.0 and allows you to open a new link even if the call uses the same parameters.
    up
    -24
    Anonymous
    10 years ago
    function go_mysql($query)
    {
        global $mysql_link;
       
        if (!$mysql_link)
        {
            $mysql_link = mysql_connect("localhost","root","my_pass") or die(mysql_error());
            mysql_select_db("my_db") or die(mysql_error());
            mysql_query("SET NAMES 'utf8'");
            mysql_query("set character_set_client='utf8'");
            mysql_query("set character_set_results='utf8'");
            mysql_query("set collation_connection='utf8'");
            global $mysql_link;
        }
           
        $result=mysql_query($query);
        if ($result)
        {
            return $result;
        }
        else
        {
            echo "Database Error: " . mysql_error()."<br><b>$query</b>";
            die();
        }
    }
    up
    -23
    anotheruser at example dot com
    15 years ago
    Cross-database join queries, expanding on Dan Ross's post...

    Really, this is a mysql specific feature, but worth noting here.  So long as the mysql user has been given the right permissions to all databases and tables where data is pulled from or pushed to, this will work.  Though the mysql_select_db function selects one database, the mysql statement may reference another (the syntax for referencing a field in another db table being 'database.table.field').

    <?php

    $sql_statement     = "SELECT
        PostID,
        AuthorID,
        Users.tblUsers.Username
        FROM tblPosts
        LEFT JOIN Users.tblUsers ON AuthorID = Users.tblUsers.UserID
        GROUP BY PostID,AuthorID,Username
        "    ;

    $dblink = mysql_connect("somehost", "someuser", "password");
    mysql_select_db("BlogPosts",$dblink);
    $qry = mysql_query($sql_statement,$dblink);

    ?>
    up
    -30
    miloshio at gmail dot com
    11 years ago
    You can select MySQL database without using this function.
    Simply right after connecting to MySQL
    <?php $connection = mysql_connect("dabatbasehost", "username", "password"); ?>
    perform this query:
    <?php mysql_query("USE somedatabase", $connection); ?>
    up
    -30
    duncan at berrimans dot co dot uk
    12 years ago
    Note that the manual is slightly misleading it states :-

    "Sets the current active database on the server that's associated with the specified link identifier. Every subsequent call to mysql_query() will be made on the active database."

    The 2nd statement is not true or at best unclear.

    mysql_query() manual entry actually correctly states it will use the last link opened by mysql_connect() by default.

    Thus if you have 2 connections you will need to specify the connection when calling mysql_query or issue the connect again to ensure the 1st database becomes the default, simply using mysql_select_db will not make the 1st database the default for subsequent calls to mysql_query.

    Its probably only apparent when the two databases are on different servers.
    up
    -34
    me at khurshid dot com
    16 years ago
    Problem with connecting to multiple databases within the same server is that every time you do:
    mysql_connect(host, username, passwd);
    it will reuse 'Resource id' for every connection, which means you will end with only one connection reference to avoid that do:
    mysql_connect(host, username, passwd, true);
    keeps all connections separate.
    up
    -57
    riad93 at mail dot ru
    14 years ago
    You can use DataBases without <?php mysql_select_db() ?>

    And you will havenot james at gogo dot co dot nz's problems :)

    <?php
    mysql_connect    ('localhost','db_user','pssword');
    mysql_query('SELECT * FROM database_name.table_name');

    ?>
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