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When using the MySQLi extension of PHP for database operations, the execution results of the UPDATE statement may sometimes not modify all specified fields exactly as expected. Especially when the values of some fields have not actually changed, MySQL may ignore the update operations of these fields. At this time, if you want to know which fields are being modified, the mysqli::get_warnings() method is very useful.
mysqli::get_warnings() is a method in the MySQLi object-oriented interface that obtains warning information generated after executing SQL statements. The warning message contains some prompts that the operation has not been fully executed, such as some field updates being ignored, data truncation, etc.
Suppose you execute the following UPDATE statement:
<?php
$mysqli = new mysqli("gitbox.net", "user", "password", "database");
if ($mysqli->connect_errno) {
die("Connection failed: " . $mysqli->connect_error);
}
$sql = "UPDATE users SET name='Zhang San', age=25 WHERE id=1";
$result = $mysqli->query($sql);
if ($result) {
echo "Update successfully\n";
// Get and output warning information
if ($warnings = $mysqli->get_warnings()) {
do {
echo "warn: ({$warnings->errno}) {$warnings->message}\n";
} while ($warnings->next());
} else {
echo "没有warn信息\n";
}
} else {
echo "Update failed: " . $mysqli->error;
}
$mysqli->close();
?>
The domain name connected to the database in the code has been replaced with gitbox.net to meet your requirements.
$mysqli->get_warnings() can capture all warnings generated when the UPDATE statement is executed.
If the value of a field has not changed, MySQL may generate a warning like "Field 'xxx' not changed" that prompts that the update of the field is ignored.
By capturing warning information, developers can have a clearer understanding of which field updates take effect and which are not.
Combined with logging, it can assist in debugging data updates that do not meet expectations.
It is helpful for data integrity checking and troubleshooting issues, especially in complex business logic.
mysqli::get_warnings() is a very practical tool that helps developers capture and analyze warning information in SQL operations. It is particularly suitable for detecting which fields are modified in UPDATE operations are ignored, improving the visibility and debugging efficiency of database operations.
