PHP mysqli select_db() Method

The PHP mysqli::select_db() / mysqli_select_db() function is used to select the default database to be used when performing queries against the database connection.

Note: This function should only be used to change the default database for the connection. It can also be selected using default database as fourth parameter in mysqli_connect() function.

Syntax

//Object-oriented style
public mysqli::select_db(database)

//Procedural style
mysqli_select_db(mysql, database)

Parameters

`mysql`	`Required.` For procedural style only: Specify a mysqli object returned by mysqli_connect() or mysqli_init().
`database`	`Required.` Specify the database name.

Return Value

Returns true on success or false on failure.

Example: Object-oriented style

The example below shows the usage of mysqli::select_db() method.

<?php
//establishing connection to the database
$mysqli = new mysqli("localhost", "user", "password", "myDb1");
if ($mysqli->connect_errno) {
  echo "Connection error: ". $mysqli->connect_errno;
  exit();
}

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

//changing default database to "myDb2"
$mysqli->select_db("myDb2");

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

//closing the connection
$mysqli->close();
?>

The output of the above code will be:

Default database is myDb1.
Default database is myDb2.

Example: Procedural style

The example below shows the usage of mysqli_select_db() function.

<?php
//establishing connection to the database
$mysqli = mysqli_connect("localhost", "user", "password", "myDb1");
if (mysqli_connect_errno()) {
  echo "Connection error: ". mysqli_connect_errno();
  exit();
}

//getting the name of the current default database
$result = mysqli_query($mysqli, "SELECT DATABASE()");
$row = mysqli_fetch_row($result);
printf("Default database is %s.\n", $row[0]);

//changing default database to "myDb2"
mysqli_select_db($mysqli, "myDb2");

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

//closing the connection
mysqli_close($mysqli);
?>

The output of the above code will be:

Default database is myDb1.
Default database is myDb2.

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