How to determine if sql is not empty in php

php method to determine that sql is not empty: first find out the information through the sql query function code; then obtain the number of rows in the select result set through "mysql_query" in the php file; finally determine the sql query results through the if statement That’s it.

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PHP and mysql, the golden partners, work well together, but Occasionally, I will encounter some small needs and I don’t know what to do. For example, what I’m going to talk about today: How to determine whether the result set of a SQL statement query is empty!

Let’s take querying student information as an example to see how to achieve our needs.

First of all, let’s take a look at what the data stored in our data table “student” looks like; 3

2 Li Sinan 15 18 2

3 Wang Meili 16 17 5

Let’s take a look at the sql query function code. We want to add the student information of 16 years old Find them all;

<?php$sql = "select * from `student` where `age`=&#39;16&#39;;";$rows = mysql_query($rs);?>
<ul>
    <?php        while($rows=mysql_fetch_array($rs)){    ?>
        <li>姓名：<?php echo $rows[&#39;stuname&#39;];?></li>
        <li>性别：<?php echo $rows[&#39;gender&#39;];?></li>
        <li>年龄：<?php echo $rows[&#39;age&#39;];?></li>
        <li>年级：<?php echo $rows[&#39;grade&#39;];?></li>
        <li>班级：<?php echo $rows[&#39;class&#39;];?></li>
    <?php
        }    ?>
</ul>

The above is the query function. When the result set is not empty, everything is normal. When the data set is empty, you will get a

blank ul tag

, As a user, I don’t knowwhy I didn’t get the data. At this time, we need to

give the user a prompt message, then we need to determine whether this result set is empty! How to determine whether the result set is empty? There are two methods:

<?php
//方法一 获取select结果集的行数
$rows=mysql_query("select * from `student` where `age`=&#39;16&#39;;");
if (mysql_num_rows($rows) < 1){
echo &#39;查询无数据！&#39;;
}

//方法二 返回上一次操作受影响的行数
$rows=mysql_query("select * from `student` where `age`=&#39;16&#39;;");
if(!mysql_affected_rows()){
    echo &#39;查询无数据！&#39;;
}
?>知道了方法，那么把方法套到我们的代码中看看效果吧

//方法一
<?php
$sql = "select * from `student` where `age`=&#39;16&#39;;";
$rows = mysql_query($rs);
?>
<ul>
    <?php
    if (mysql_num_rows($rs) < 1){
        echo &#39;查询无数据！&#39;;
    }else{
        while($rows=mysql_fetch_array($rs)){
    ?>
        <li>姓名：<?php echo $rows[&#39;stuname&#39;];?></li>
        <li>性别：<?php echo $rows[&#39;gender&#39;];?></li>
        <li>年龄：<?php echo $rows[&#39;age&#39;];?></li>
        <li>年级：<?php echo $rows[&#39;grade&#39;];?></li>
        <li>班级：<?php echo $rows[&#39;class&#39;];?></li>
    <?php
        }
    }
    ?>
</ul>

//方法二
<?php
$sql = "select * from `student` where `age`=&#39;16&#39;;";
$rows = mysql_query($rs);
?>
<ul>
    <?php
    if(mysql_affected_rows()){
        while ($rows=mysql_fetch_assoc($rs)){
    ?>
        <li>姓名：<?php echo $rows[&#39;stuname&#39;];?></li>
        <li>性别：<?php echo $rows[&#39;gender&#39;];?></li>
        <li>年龄：<?php echo $rows[&#39;age&#39;];?></li>
        <li>年级：<?php echo $rows[&#39;grade&#39;];?></li>
        <li>班级：<?php echo $rows[&#39;class&#39;];?></li>
    <?php
        }
    }else {
        echo "查无数据！";
    }
    ?>
</ul>

OK, you’re done. Now you will get a prompt when no data can be found!

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