PHP MySQL Where
The WHERE clause is used to filter records, which is to query the data under our specified conditions
Syntax
Basic syntax select field from table where where condition; Exampleselect * from money where age = 29; Example descriptionQuery all results with age 29 in the MyGuests tableLet us use the following example:
Example
The following example will select all FirstNames from the "MyGuests" table ='Mary' row:
<?php
header("Content-type:text/html;charset=utf-8"); //设置编码
$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "test";
$con=mysqli_connect($servername, $username, $password, $dbname);
// 检测连接
if (mysqli_connect_errno())
{
echo "连接失败: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT * FROM MyGuests
WHERE FirstName='Mary'");
while($row = mysqli_fetch_array($result))
{
echo $row['firstname'] . "----" . $row['lastname'] ."----".$row['email'];
echo "<br>";
}
?>Program execution result:
Use where condition to query all the data of FirstName='Mary' come out.
We now use phpadmin to add an Age field to the MyGuests table
The data in the table now looks like this:
Example
We now use the where clause to query those with Age less than 25:
<?php
header("Content-type:text/html;charset=utf-8"); //设置编码
$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "test";
$con=mysqli_connect($servername, $username, $password, $dbname);
// 检测连接
if (mysqli_connect_errno())
{
echo "连接失败: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT * FROM MyGuests
WHERE Age<25 ");
while($row = mysqli_fetch_array($result))
{
echo $row['firstname'] . "----" . $row['lastname'] ."----".$row['email']."----".$row['Age'];
echo "<br>";
}
?>Program running results:
You can also use the following conditions
| ## Type | Detailed explanation |
| Symbol | Description |
| Greater than or equal to | |
| Less than or equal to |
Logical operators
## or Or and And Let’s take a look at an example of multiple conditions:| ## Symbol | Description |
We query the data of 'firstname'='Julie' and Age=24
<?php
header("Content-type:text/html;charset=utf-8"); //设置编码
$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "test";
$con=mysqli_connect($servername, $username, $password, $dbname);
// 检测连接
if (mysqli_connect_errno())
{
echo "连接失败: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT * FROM MyGuests
WHERE Firstname='Julie' AND Age=24 ");
while($row = mysqli_fetch_array($result))
{
echo $row['firstname'] . "----" . $row['lastname'] ."----".$row['email']."----".$row['Age'];
echo "<br>";
}
?>Program running results: 
