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PHP mysqli: select_db() function

mysqli_select_db() function/ mysqli::select_db

The mysqli_select_db() function/ mysqli::select_db is used to change the default database for the connection.

Syntax:

Object oriented style

bool mysqli::select_db ( string $dbname )

Procedural style

bool mysqli_select_db ( mysqli $link , string $dbname )

Parameter:

Name Description Required/Optional
link A link identifier returned by mysqli_connect() or mysqli_init() Required for procedural style only and Optional for Object oriented style
dbname The database name. Required

Usage: Procedural style

mysqli_select_db(connection,dbname);

Parameter:

Name Description Required/Optional
connection Specifies the MySQL connection to use Required
dbname Specifies the default database to be used Required

Return value:

Returns TRUE on success or FALSE on failure.

Version: PHP 5, PHP 7

Example of object oriented style:

<?php
$mysqli = new mysqli("localhost", "user1", "datasoft123", "hr");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("Default database is %s.\n", $row[0]);
    $result->close();
}

/* change db to world db */
$mysqli->select_db("hr");

/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("Default database is %s.\n", $row[0]);
    $result->close();
}

$mysqli->close();
?>

Output:

Default database is hr. Default database is hr.

Example of the Procedural style

<?php
$link = mysqli_connect("localhost", "user1", "datasoft123", "hr");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    printf("Default database is %s.\n", $row[0]);
    mysqli_free_result($result);
}

/* change db to world db */
mysqli_select_db($link, "hr");

/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    printf("Default database is %s.\n", $row[0]);
    mysqli_free_result($result);
}

mysqli_close($link);
?>

Output:

Default database is hr.
Default database is hr.

See also

PHP Function Reference

Previous: rollback
Next: set_charset



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PHP: Tips of the Day

To use the constant simply use its name:

Example:

if (EARTH_IS_FLAT) {
 print "Earth is flat";
}
print APP_ENV_UPPERCASE;

Output:



or if you don't know the name of the constant in advance, use the constant function:


// this code is equivalent to the above code
$const1 = "EARTH_IS_FLAT";
$const2 = "APP_ENV_UPPERCASE";
if (constant($const1)) {
 print "Earth is flat";
}
print constant($const2);



Output:




 


























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