mysqli

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

Posted on by user

MySQLi – Select Query

The SQL SELECT command is used to fetch data from the MySQL database. You can use this command at mysql> prompt as well as in any script like PHP.

Syntax

Here is generic SQL syntax of SELECT command to fetch data from the MySQL table −

SELECT field1, field2,...fieldN 
FROM table_name1, table_name2...
[WHERE Clause]
[OFFSET M ][LIMIT N]

  • You can use one or more tables separated by comma to include various conditions using a WHERE clause, but the WHERE clause is an optional part of the SELECT command.

  • You can fetch one or more fields in a single SELECT command.

  • You can specify star (*) in place of fields. In this case, SELECT will return all the fields.

  • You can specify any condition using the WHERE clause.

  • You can specify an offset using OFFSET from where SELECT will start returning records. By default, the offset starts at zero.

  • You can limit the number of returns using the LIMIT attribute.

Fetching Data from a Command Prompt

This will use SQL SELECT command to fetch data from the MySQL table tutorials_tbl.

Example

The following example will return all the records from the tutorials_tbl table −

root@host# mysql -u root -p password;
Enter password:*******
mysql> use TUTORIALS;
Database changed
mysql> SELECT * from tutorials_tbl 
+-------------+----------------+-----------------+-----------------+
| tutorial_id | tutorial_title | tutorial_author | submission_date |
+-------------+----------------+-----------------+-----------------+
|           1 | Learn PHP      | John Poul       | 2007-05-21      |
|           2 | Learn MySQL    | Abdul S         | 2007-05-21      |
|           3 | JAVA Tutorial  | Sanjay          | 2007-05-21      |
+-------------+----------------+-----------------+-----------------+
3 rows in set (0.01 sec)

mysql>

Fetching Data Using a PHP Script

PHP uses mysqli query() or mysql_query() function to select records from 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 select records from 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.

Example

Try the following example to select a record from 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 = "SELECT tutorial_id, tutorial_title, tutorial_author, submission_date FROM tutorials_tbl";
		 
         $result = $mysqli->query($sql);
           
         if ($result->num_rows > 0) {
            while($row = $result->fetch_assoc()) {
               printf("Id: %s, Title: %s, Author: %s, Date: %d <br />", 
                  $row["tutorial_id"], 
                  $row["tutorial_title"], 
                  $row["tutorial_author"],
                  $row["submission_date"]);               
            }
         } else {
            printf(''No record found.<br />'');
         }
         mysqli_free_result($result);
         $mysqli→close();
      ?>
   </body>
</html>

Output

Access the mysql_example.php deployed on apache web server and verify the output. Here we”ve entered multiple records in the table before running the select script.

Connected successfully.
Id: 1, Title: MySQL Tutorial, Author: Mahesh, Date: 2021
Id: 2, Title: HTML Tutorial, Author: Mahesh, Date: 2021
Id: 3, Title: PHP Tutorial, Author: Mahesh, Date: 2021
Id: 4, Title: Java Tutorial, Author: Mahesh, Date: 2021
Id: 5, Title: Apache Tutorial, Author: Suresh, Date: 2021

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

user