PHP | MySQL WHERE Clause

03 Mar, 2018
The WHERE Clause is used to filter only those records that are fulfilled by a specific condition given by the user. in other words, the SQL WHERE clause is used to restrict the number of rows affected by a SELECT, UPDATE or DELETE query.
Syntax :The basic syntax of the where clause is –SELECT Column1 , Column2 , ....FROM Table_NameWHERE Condition
Let us consider the following table “Data” with three columns ‘FirstName’, ‘LastName’ and ‘Age’.
To select all the rows where the “Firstname” is “ram”, we will use the following code :
Where Clause using Procedural Method :
<?php$link = mysqli_connect("localhost", "root", "", "Mydb");  if($link === false){    die("ERROR: Could not connect. "                . mysqli_connect_error());}  $sql = "SELECT * FROM Data WHERE Firstname='ram'";if($res = mysqli_query($link, $sql)){    if(mysqli_num_rows($res) > 0){        echo "<table>";            echo "<tr>";                echo "<th>Firstname</th>";                echo "<th>Lastname</th>";                echo "<th>age</th>";            echo "</tr>";        while($row = mysqli_fetch_array($res)){            echo "<tr>";                echo "<td>" . $row['Firstname'] . "</td>";                echo "<td>" . $row['Lastname'] . "</td>";                echo "<td>" . $row['Age'] . "</td>";            echo "</tr>";        }        echo "</table>";        mysqli_free_result($res);    } else{        echo "No Matching records are found.";    }} else{    echo "ERROR: Could not able to execute $sql. "                                 . mysqli_error($link);}  mysqli_close($link);?>
Output :
Code Explanation :
The “res” variable stores the data that is returned by the function mysql_query().Everytime mysqli_fetch_array() is invoked, it returns the next row from the res() set.The while loop is used to loop through all the rows of the table “data”.
The “res” variable stores the data that is returned by the function mysql_query().
Everytime mysqli_fetch_array() is invoked, it returns the next row from the res() set.
The while loop is used to loop through all the rows of the table “data”.
Where Clause using Object Oriented Method :
<?php$mysqli = new mysqli("localhost", "root", "", "Mydb");  if($mysqli === false){    die("ERROR: Could not connect. "                 . $mysqli->connect_error);}  $sql = "SELECT * FROM Data WHERE Firstname='ram'";if($res = $mysqli->query($sql)){    if($res->num_rows > 0){        echo "<table>";            echo "<tr>";                echo "<th>Firstname</th>";                echo "<th>Lastname</th>";                echo "<th>Age</th>";            echo "</tr>";        while($row = $res->fetch_array()){            echo "<tr>";                echo "<td>" . $row['Firstname'] . "</td>";                echo "<td>" . $row['Lastname'] . "</td>";                echo "<td>" . $row['Age'] . "</td>";            echo "</tr>";        }        echo "</table>";        $res->free();    } else{        echo "No matching records are found.";    }} else{    echo "ERROR: Could not able to execute $sql. "                                     . $mysqli->error;}  $mysqli->close();?>
Output :
Where Clause using PDO Method :
<?phptry{    $pdo = new PDO("mysql:host=localhost;                    dbname=Mydb", "root", "");    $pdo->setAttribute(PDO::ATTR_ERRMODE,                         PDO::ERRMODE_EXCEPTION);} catch(PDOException $e){    die("ERROR: Could not connect. "                     . $e->getMessage());}  try{    $sql = "SELECT * FROM Data WHERE Firstname='ram'";     $res = $pdo->query($sql);    if($res->rowCount() > 0){        echo "<table>";            echo "<tr>";                echo "<th>Firstname</th>";                echo "<th>Lastname</th>";                echo "<th>Age</th>";            echo "</tr>";        while($row = $res->fetch()){            echo "<tr>";                echo "<td>" . $row['Firstname'] . "</td>";                echo "<td>" . $row['Lastname'] . "</td>";                echo "<td>" . $row['Age'] . "</td>";            echo "</tr>";        }        echo "</table>";        unset($res);    } else{        echo "No records matching are found.";    }} catch(PDOException $e){    die("ERROR: Could not able to execute $sql. "                                    . $e->getMessage());}  unset($pdo);?>
Output :
mysql
PHP
SQL
Web Technologies
SQL
PHP
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
How to Insert Form Data into Database using PHP ?
How to convert array to string in PHP ?
How to Upload Image into Database and Display it using PHP ?
How to check whether an array is empty using PHP?
PHP | Converting string to Date and DateTime
SQL | DDL, DQL, DML, DCL and TCL Commands
SQL | Join (Inner, Left, Right and Full Joins)
SQL | WITH clause
How to find Nth highest salary from a table
CTE in SQL