Category: mysqli

Khóa học miễn phí MySQLi – Select Database nhận dự án làm có lương

MySQLi – Select Database

Once you get connected with the MySQL server, it is required to select a database to work with. This is because there might be more than one database available with the MySQL Server.

Selecting MySQL Database from the Command Prompt

It is very simple to select a database from the mysql> prompt. You can use the SQL command use to select a database.

Example

Here is an example to select a database called TUTORIALS −

[root@host]# mysql -u root -p
Enter password:******
mysql> use TUTORIALS;
Database changed
mysql>

Now, you have selected the TUTORIALS database and all the subsequent operations will be performed on the TUTORIALS database.

NOTE − All the database names, table names, table fields name are case sensitive. So you would have to use the proper names while giving any SQL command.

Selecting a MySQL Database Using PHP Script

PHP uses mysqli_select_db function to select the database on which queries are to be performed. This function takes two parameters and returns TRUE on success or FALSE on failure.

Syntax

mysqli_select_db ( mysqli $link , string $dbname ) : bool

Sr.No.	Parameter & Description
1	$link Required – A link identifier returned by mysqli_connect() or mysqli_init().
2	$dbname Required – Name of the database to be connected.

Sr.No.

Parameter & Description

$link

Required – A link identifier returned by mysqli_connect() or mysqli_init().

$dbname

Required – Name of the database to be connected.

Example

Try the following example to select a database −

Copy and paste the following example as mysql_example.php −

<html>
   <head>
      <title>Selecting MySQL Database</title>
   </head>
   <body>
   <?php
      $dbhost = ''localhost
      $dbuser = ''root
      $dbpass = ''root@123
      $conn = mysqli_connect($dbhost, $dbuser, $dbpass);

      if(! $conn ) {
         die(''Could not connect: '' . mysqli_error($conn));
      }
      echo ''Connected successfully<br />

      $retval = mysqli_select_db( $conn, ''TUTORIALS'' );

      if(! $retval ) {
         die(''Could not select database: '' . mysqli_error($conn));
      }
      echo "Database TUTORIALS selected successfullyn";
      mysqli_close($conn);
   ?>
   </body>
</html>

Output

Access the mysql_example.php deployed on apache web server and verify the output.

Database TUTORIALS selected successfully

Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

August 17, 2024

Khóa học miễn phí MySQLi – Connection nhận dự án làm có lương

MySQLi – Connection

MySQL Connection Using MySQL Binary

You can establish the MySQL database using the mysql binary at the command prompt.

Example

Here is a simple example to connect to the MySQL server from the command prompt −

[root@host]# mysql -u root -p
Enter password:******

This will give you the mysqli command prompt where you will be able to execute any SQL command. Following is the result of above command −

The following code block shows the result of above code −

Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 2854760 to server version: 5.0.9

Type ''help;'' or ''h'' for help. Type ''c'' to clear the buffer.

In the above example, we have used root as a user but you can use any other user as well. Any user will be able to perform all the SQL operations, which are allowed to that user.

You can disconnect from the MySQL database any time using the exit command at mysql> prompt.

mysql> exit
Bye

MySQL Connection Using PHP Script

PHP provides mysqli contruct or mysqli_connect() function to open a database connection. This function takes six parameters and returns a MySQL link identifier on success or FALSE on failure.

Syntax

$mysqli = new mysqli($host, $username, $passwd, $dbName, $port, $socket);

Sr.No.	Parameter & Description
1	$host Optional − The host name running the database server. If not specified, then the default value will be localhost:3306.
2	$username Optional − The username accessing the database. If not specified, then the default will be the name of the user that owns the server process.
3	$passwd Optional − The password of the user accessing the database. If not specified, then the default will be an empty password.
4	$dbName Optional − database name on which query is to be performed.
5	$port Optional − the port number to attempt to connect to the MySQL server..
6	$socket Optional − socket or named pipe that should be used.

You can disconnect from the MySQL database anytime using another PHP function close().

Syntax

$mysqli→close();

Example

Try the following example to connect to a MySQL server −

Copy and paste the following example as mysql_example.php −

<html>
   <head>
      <title>Connecting MySQL Server</title>
   </head>
   <body>
      <?php
         $dbhost = ''localhost
         $dbuser = ''root
         $dbpass = ''root@123
         $mysqli = new mysqli($dbhost, $dbuser, $dbpass);

         if($mysqli→connect_errno ) {
            printf("Connect failed: %s<br />", $mysqli→connect_error);
            exit();
         }
         printf(''Connected successfully.<br />'');
         $mysqli→close();
      ?>
   </body>
</html>

Output

Access the mysql_example.php deployed on apache web server and verify the output.

Connected successfully.

Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

August 17, 2024

Khóa học miễn phí MySQLi – Create Tables nhận dự án làm có lương

MySQLi – Create Table

To begin with, the table creation command requires the following details −

Name of the table
Name of the fields
Definitions for each field

Syntax

Here is a generic SQL syntax to create a MySQL table −

CREATE TABLE table_name (column_name column_type);

Now, we will create the following table in the TUTORIALS database.

create table tutorials_tbl(
   tutorial_id INT NOT NULL AUTO_INCREMENT,
   tutorial_title VARCHAR(100) NOT NULL,
   tutorial_author VARCHAR(40) NOT NULL,
   submission_date DATE,
   PRIMARY KEY ( tutorial_id )
);

Here, a few items need explanation −

Field Attribute NOT NULL is being used because we do not want this field to be NULL. So, if a user will try to create a record with a NULL value, then MySQL will raise an error.
Field Attribute AUTO_INCREMENT tells MySQL to go ahead and add the next available number to the id field.
Keyword PRIMARY KEY is used to define a column as a primary key. You can use multiple columns separated by a comma to define a primary key.

Creating Tables from Command Prompt

It is easy to create a MySQL table from the mysql> prompt. You will use the SQL command CREATE TABLE to create a table.

Example

Here is an example, which will create tutorials_tbl −

root@host# mysql -u root -p
Enter password:*******
mysql> use TUTORIALS;
Database changed
mysql> CREATE TABLE tutorials_tbl(
   → tutorial_id INT NOT NULL AUTO_INCREMENT,
   → tutorial_title VARCHAR(100) NOT NULL,
   → tutorial_author VARCHAR(40) NOT NULL,
   → submission_date DATE,
   → PRIMARY KEY ( tutorial_id )
   → );
Query OK, 0 rows affected (0.16 sec)
mysql>

NOTE − MySQL does not terminate a command until you give a semicolon (;) at the end of SQL command.

Creating Tables Using PHP Script

PHP uses mysqli query() or mysql_query() function to create a MySQL table. This function takes two parameters and returns TRUE on success or FALSE on failure.

Syntax

$mysqli→query($sql,$resultmode)

Sr.No.	Parameter & Description
1	$sql Required – SQL query to create a MySQL table.
2	$resultmode Optional – Either the constant MYSQLI_USE_RESULT or MYSQLI_STORE_RESULT depending on the desired behavior. By default, MYSQLI_STORE_RESULT is used.

Sr.No.

Parameter & Description

$sql

Required – SQL query to create a MySQL table.

$resultmode

Optional – Either the constant MYSQLI_USE_RESULT or MYSQLI_STORE_RESULT depending on the desired behavior. By default, MYSQLI_STORE_RESULT is used.

Example

Try the following example to create a table −

Copy and paste the following example as mysql_example.php −

<html>
   <head>
      <title>Creating MySQL Table</title>
   </head>
   <body>
      <?php
         $dbhost = ''localhost
         $dbuser = ''root
         $dbpass = ''root@123
         $dbname = ''TUTORIALS
         $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);

         if($mysqli→connect_errno ) {
            printf("Connect failed: %s<br />", $mysqli→connect_error);
            exit();
         }
         printf(''Connected successfully.<br />'');

         $sql = "CREATE TABLE tutorials_tbl( ".
            "tutorial_id INT NOT NULL AUTO_INCREMENT, ".
            "tutorial_title VARCHAR(100) NOT NULL, ".
            "tutorial_author VARCHAR(40) NOT NULL, ".
            "submission_date DATE, ".
            "PRIMARY KEY ( tutorial_id )); ";
         if ($mysqli→query($sql)) {
            printf("Table tutorials_tbl created successfully.<br />");
         }
         if ($mysqli→errno) {
            printf("Could not create table: %s<br />", $mysqli→error);
         }
         $mysqli→close();
      ?>
   </body>
</html>

Output

Access the mysql_example.php deployed on apache web server and verify the output.

Connected successfully.
Table tutorials_tbl created successfully.

Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

August 17, 2024

Khóa học miễn phí MySQLi – Insert Query nhận dự án làm có lương

MySQLi – Insert Query

To insert data into a MySQL table, you would need to use the SQL INSERT INTO command. You can insert data into the MySQL table by using the mysql> prompt or by using any script like PHP.

Syntax

Here is a generic SQL syntax of INSERT INTO command to insert data into the MySQL table −

INSERT INTO table_name ( field1, field2,...fieldN )
   VALUES
   ( value1, value2,...valueN );

To insert string data types, it is required to keep all the values into double or single quotes. For example “value”.

Inserting Data from the Command Prompt

To insert data from the command prompt, we will use SQL INSERT INTO command to insert data into MySQL table tutorials_tbl.

Example

The following example will create 3 records into tutorials_tbl table −

root@host# mysql -u root -p password;
Enter password:*******
mysql> use TUTORIALS;
Database changed

mysql> INSERT INTO tutorials_tbl
   →(tutorial_title, tutorial_author, submission_date)
   →VALUES
   →("Learn PHP", "John Poul", NOW());
Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO tutorials_tbl
   →(tutorial_title, tutorial_author, submission_date)
   →VALUES
   →("Learn MySQL", "Abdul S", NOW());
Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO tutorials_tbl
   →(tutorial_title, tutorial_author, submission_date)
   →VALUES
   →("JAVA Tutorial", "Sanjay", ''2007-05-06'');
Query OK, 1 row affected (0.01 sec)
mysql>

NOTE − Please note that all the arrow signs (→) are not a part of the SQL command. They are indicating a new line and they are created automatically by the MySQL prompt while pressing the enter key without giving a semicolon at the end of each line of the command.

In the above example, we have not provided a tutorial_id because at the time of table creation, we had given AUTO_INCREMENT option for this field. So MySQL takes care of inserting these IDs automatically. Here, NOW() is a MySQL function, which returns the current date and time.

Inserting Data Using a PHP Script

PHP uses mysqli query() or mysql_query() function to insert a record into a MySQL table. This function takes two parameters and returns TRUE on success or FALSE on failure.

Syntax

$mysqli→query($sql,$resultmode)

Sr.No.	Parameter & Description
1	$sql Required – SQL query to insert record into a table.
2	$resultmode Optional – Either the constant MYSQLI_USE_RESULT or MYSQLI_STORE_RESULT depending on the desired behavior. By default, MYSQLI_STORE_RESULT is used.

Sr.No.

Parameter & Description

$sql

Required – SQL query to insert record into a table.

$resultmode

Optional – Either the constant MYSQLI_USE_RESULT or MYSQLI_STORE_RESULT depending on the desired behavior. By default, MYSQLI_STORE_RESULT is used.

Example

This example will take three parameters from the user and will insert them into the MySQL table − −

Copy and paste the following example as mysql_example.php −

<html>
   <head>
      <title>Add New Record in MySQL Database</title>
   </head>
   <body>
      <?php
         if(isset($_POST[''add''])) {
            $dbhost = ''localhost
            $dbuser = ''root
            $dbpass = ''root@123
            $dbname = ''TUTORIALS
            $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);

            if($mysqli→connect_errno ) {
               printf("Connect failed: %s<br />", $mysqli→connect_error);
               exit();
            }
            printf(''Connected successfully.<br />'');

            if(! get_magic_quotes_gpc() ) {
               $tutorial_title = addslashes ($_POST[''tutorial_title'']);
               $tutorial_author = addslashes ($_POST[''tutorial_author'']);
            } else {
               $tutorial_title = $_POST[''tutorial_title''];
               $tutorial_author = $_POST[''tutorial_author''];
            }
            $submission_date = $_POST[''submission_date''];
            $sql = "INSERT INTO tutorials_tbl ".
               "(tutorial_title,tutorial_author, submission_date) "."VALUES ".
               "(''$tutorial_title'',''$tutorial_author'',''$submission_date'')";

            if ($mysqli→query($sql)) {
               printf("Record inserted successfully.<br />");
            }
            if ($mysqli→errno) {
               printf("Could not insert record into table: %s<br />", $mysqli→error);
            }
            $mysqli→close();
         } else {
      ?>
      <form method = "post" action = "<?php $_PHP_SELF ?>">
         <table width = "600" border = "0" cellspacing = "1" cellpadding = "2">
            <tr>
               <td width = "250">Tutorial Title</td>
               <td><input name = "tutorial_title" type = "text" id = "tutorial_title"></td>
            </tr>
            <tr>
               <td width = "250">Tutorial Author</td>
               <td><input name = "tutorial_author" type = "text" id = "tutorial_author"></td>
            </tr>
            <tr>
               <td width = "250">Submission Date [   yyyy-mm-dd ]</td>
               <td><input name = "submission_date" type = "text" id = "submission_date"></td>
            </tr>
            <tr>
               <td width = "250"> </td>
               <td></td>
            </tr>
            <tr>
               <td width = "250"> </td>
               <td><input name = "add" type = "submit" id = "add"  value = "Add Tutorial"></td>
            </tr>
         </table>
      </form>
   <?php
      }
   ?>
   </body>
</html>

Output

Access the mysql_example.php deployed on apache web server, enter details and verify the output on submitting the form.

Record inserted successfully.

While doing a data insert, it is best to use the function get_magic_quotes_gpc() to check if the current configuration for magic quote is set or not. If this function returns false, then use the function addslashes() to add slashes before the quotes.

You can put many validations around to check if the entered data is correct or not and can take the appropriate action.

Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

August 17, 2024