How to get sql query results in php

PHP is a widely used web development language that can be integrated with the MySQL database to retrieve, modify, update and delete data through SQL query language. In PHP, getting the results of a SQL query is very important because you can determine whether the execution of the script was successful and what our next actions will be.

This article will introduce how to get SQL query results in PHP. We will discuss the following aspects:

1. Establishing a connection to the database
2. Setting up SQL queries Statement
3. Execute SQL query
4. Process the query results
5. Establish a connection with the database

In PHP, you must first establish a connection with the MySQL database Connection to facilitate execution of SQL query statements. You can use the following code snippet to establish a connection to the database:

<?php  
$con = mysqli_connect("localhost","root","","mydatabase");  
if (!$con) {  
  die('Could not connect: ' . mysqli_connect_error());  
}  
?>

Here "localhost" represents the host name of the database server, "root" represents the database administrator user name, and "mydatabase" represents the database we want to connect to. Name database.

2. Set the SQL query statement

Next, we need to set the SQL query statement. In PHP, you can use the mysqli_query() function to perform SQL queries. The code is as follows:

$sql = "SELECT * FROM mytable";  
$result = mysqli_query($con,$sql);  

"mytable" here represents the name of the table we want to query, and "*" represents querying all columns.

3. Execute SQL query

After we set up the SQL query statement, we need to execute the query to obtain the results. You can use the mysqli_fetch_array() function to obtain query results. The code is as follows:

while($row = mysqli_fetch_array($result)) {  
  echo $row['id'] . ' ' . $row['name'];  
  echo '<br>';  
}

In this example, we use a while loop to obtain the query results one by one. The mysqli_fetch_array() function returns an array containing the next row of data, where the keys are column names or column numbers. We use $row['id'] and $row['name'] to output the results.

4. Processing query results

After we obtain the query results, we may need to perform further processing based on the results, such as outputting the results or checking whether the query was successfully executed. The following code demonstrates how to check whether the query is executed successfully:

if ($result->num_rows > 0) {  
  // 查询成功  
} else {  
  // 查询失败  
}  

In this example, we use $num_rows to check whether the query result is empty. If $num_rows is greater than 0, the query is successful, otherwise the query fails.

We can also get the number of affected rows through the mysqli_affected_rows() function. The number of affected rows is usually zero for a SELECT query and equal to the number of affected rows for an UPDATE, DELETE, or INSERT query. The code is as follows:

if(mysqli_affected_rows($con)>0) {  
  echo "操作成功";  
} else {  
  echo "操作失败";  
}  

Through the above method, we can obtain the SQL query results, check whether the query is successfully executed, and further process the data based on the results. Use the mysqli_query() function to execute SQL queries, and use the mysqli_fetch_array() function to obtain and process query results. When processing query results, we can check if $num_rows is greater than 0 and use the mysqli_affected_rows() function to get the number of affected rows. These tips can help us handle data better and bring better performance and user experience to our applications.

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