How to change multiple database data in PHP

When developing web applications, it is often necessary to modify multiple data in the database. For PHP developers, being proficient in how to change multiple data can not only improve development efficiency, but also reduce the chance of errors. This article will introduce techniques on how to change data in multiple databases in PHP.

1. Use SQL statements to change multiple data

If you need to change multiple data in the database, the easiest way is to use SQL statements to change them all at once. Multiple data can be changed by setting the WHERE clause and the SET clause of the update statement.

For example, if you want to change the status of all records in a table to "processed", you can use the following SQL statement:

UPDATE table_name SET status='已处理' WHERE 1;

where table_name is the value that needs to be changed The table name, status is the name of the status field that needs to be changed.

This SQL statement uses the UPDATE keyword to indicate that records in the table are to be updated, and the SET clause to specify the fields that need to be changed and their corresponding new values. , use the WHERE clause to specify the records that need to be changed.

It should be noted that 1 is used in the WHERE clause of this SQL statement, which is a condition that is always true. This will match all records in the table and change their status to Processed.

2. Use foreach loop to change multiple data

In addition to using SQL statements, we can also use PHP’s foreach loop to change multiple data.

Suppose there is an array $data, each element of which corresponds to the primary key of a database record and the field that needs to be changed and its corresponding new value. We can use the following code to batch change these records:

foreach ($data as $id => $values) {
    foreach ($values as $field => $value) {
        // 使用更新语句更新每个字段
        $sql = "UPDATE table_name SET $field='$value' WHERE id='$id'";
        // 执行更新语句
        $result = mysqli_query($conn, $sql);
        // 错误处理
        if (!$result) {
            die("Error: " . mysqli_error($conn));
        }
    }
}

In this code, we use a two-level foreach loop. The first level loop traverses each element in the $data array. , the second layer loops through the fields that need to be changed and the corresponding new values ​​in each element.

In the inner loop, we use an update statement to change the value of each field. It should be noted that $id is used in the update statement to specify the primary key value of the record that needs to be changed.

3. Use batch update statements to change multiple data

In addition to the above two methods, you can also use batch update statements (Batch Update) to change multiple data. This method is suitable for situations where multiple fields need to be updated at the same time.

For example, if you want to change the status and scores of all records in a table to new values, you can use the following code:

// 生成批量更新语句
$sql = "UPDATE table_name SET status=?, score=? WHERE 1";
$stmt = mysqli_prepare($conn, $sql);
// 绑定参数
$status = '已处理';
$score = 100;
mysqli_stmt_bind_param($stmt, "ss", $status, $score);
// 执行更新语句
mysqli_stmt_execute($stmt);

In this code, we first generate a batch update statement , which contains the fields and placeholders that need to be changed. Where ? represents a placeholder, indicating that it needs to be replaced with the actual value when the update statement is executed.

Next, we use the mysqli_prepare function to convert this SQL statement into a prepared statement. We then use the mysqli_stmt_bind_param function to bind the parameters and replace the placeholders ? with the actual values.

Finally, we use the mysqli_stmt_execute function to execute this update statement.

It should be noted that when using batch update statements, if there are many fields to be changed, you need to ensure that their order in the SQL statement is consistent with the order when binding parameters, otherwise the update will fail.

Summary

This article introduces three methods on how to change multiple database data in PHP, including using SQL statements, using foreach loops, and using batch update statements. It is necessary to choose the corresponding method according to the actual situation, and pay attention to avoid data consistency problems caused by updates.

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