How to use d function in php to query the database

In the process of developing a website, querying the database is an important link. In PHP, the d function can be used to easily operate the database. This article will introduce the use of the d function in detail to help readers quickly master the skills of querying the database.

1. Definition of d function

The d function is a PHP program library that encapsulates database access and provides convenient operation methods. The d function can connect to multiple types of databases, such as MySQL, SQL Server, Oracle, etc., allowing programmers to easily operate using SQL statements.

2. Basic usage of d function

The basic usage of d function is very simple and only requires three steps to complete:

1. Connect to the database

The method of using the d function to connect to the database is as follows:

$link = d('mysql://user:password@localhost/testdb');

This method will create a $link variable connected to the MySQL database testdb. Among them, mysql represents the type of database connected, user and password represent the user name and password to connect to the database respectively, and localhost represents the host address of the connection. The connected database name is set to testdb at the end.

2. Execute SQL statement

The method of d function to execute SQL statement is as follows:

$result = $link->query('SELECT * FROM users WHERE id = 1');

This method will execute a SELECT statement to query the id in the users table Records equal to 1. The query results are stored in the $result variable.

3. Processing query results

The method of processing query results is as follows:

while ($row = $result->fetch_assoc()) {
    echo $row['username'];
}

This method uses the fetch_assoc() method to read the query results row by row, and The data of each row is stored in the $row array, and the value of the username field is output.

The above are the basic methods of using the d function. Programmers only need to be proficient in these methods to easily perform database operations.

3. Advanced usage methods of d function

In addition to basic methods of connecting, querying and processing results, d function also provides some advanced usage methods to help programmers become more convenient operate the database.

1. Insert data in batches

In order to improve the efficiency of data insertion, you can use the method of batch inserting data:

$link->query('INSERT INTO users (username, password) VALUES ("user1", "pass1"), ("user2", "pass2"), ("user3", "pass3")');

This method uses one INSERT statement to insert multiple data. records, improving the efficiency of inserting data.

2. Transaction processing

The method of using the d function for transaction processing is as follows:

$link->begin_transaction();

$link->query('UPDATE users SET username = "newname" WHERE id = 1');
$link->query('DELETE FROM users WHERE id = 2');

$link->commit();

This method uses the begin_transaction() method to open a transaction, and then in turn Execute UPDATE and DELETE statements. If both statements are executed successfully, commit() is called to commit the transaction. If any of the statements fails to execute, call rollback() to roll back the transaction.

3. Prevent SQL injection

In order to prevent SQL injection attacks, the d function provides an escape() method, allowing programmers to escape the input data:

$username = $link->escape($_POST['username']);
$password = $link->escape($_POST['password']);

$link->query('INSERT INTO users (username, password) VALUES ("'.$username.'", "'.$password.'")');

This method can escape the data entered by the user to avoid SQL injection attacks.

4. Summary

This article introduces the use of d function in detail, including basic connection, query and result processing methods, as well as advanced batch data insertion, transaction processing and preventing SQL injection Methods. Using the d function allows programmers to conveniently operate various types of databases, improving development efficiency and program security.

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