How to use the database query builder in CakePHP?

CakePHP is an open source PHP MVC framework, which is widely used in the development of web applications. CakePHP has many features and tools, including a powerful database query builder for interactive performance databases. This query builder allows you to execute SQL queries using object-oriented syntax without having to write cumbersome SQL statements. This article will introduce how to use the database query builder in CakePHP.

1. Establishing a database connection

Before using the database query builder, you first need to establish a connection to the database in CakePHP. In the database.php file in your application's Config directory, you can configure the default database connection and other necessary information.

2. Import namespace

When using QueryBuilder in code, you need to import its namespace and PDO. You can import these namespaces by placing the following statement at the beginning of your file:

use CakeDatabaseConnection;
use CakeDatabaseQuery; 
use CakeDatabaseDriverMysql; 

3. Create a database connection

To use QueryBuilder, you need to create a database connection . First, you need to define a Connection object and configure the relevant parameters of the connection, such as database host, user name, password, database name, port number, etc.

$connection = new Connection([
    'driver' => new Mysql(),
    'host' => 'localhost',
    'port' => '3306',
    'username' => 'root',
    'password' => '',
    'database' => 'your_database_name'
   ]);

4. Create a query builder

Once the connection is successfully established, you can create a query builder to query the database.

$query = new Query($connection);

5. Query Database

Now you can use QueryBuilder to perform queries. Here are some examples:

• Select all records

$results = $query->select('*')->from('your_table')->execute()->fetchAll('assoc');

• Specify query conditions

$results = $query->select('*')->from('your_table')->where(['your_key' => 'your_value'])->execute()->fetchAll('assoc');

• Specify multiple query conditions

$results = $query->select('*')->from('your_table')->where(['your_key1' => 'your_value1', 'your_key2' => 'your_value2'])->execute() ->fetchAll('assoc');

• Specify a sorting method

$results = $query->select('*')->from('your_table')->order(['date_created' => 'desc'])->execute()->fetchAll('assoc');

6. Execute the query

Once you have constructed the database query, you need to execute it to get the results. The following is an example of executing a query:

$results = $query->execute()->fetchAll('assoc');

7. Conclusion

By using the database query builder in CakePHP, you no longer need to write tedious SQL statements and consume time and energy. You can easily perform operations such as data query and retrieval. The methods provided above are the basic methods of using QueryBuilder. There are many other usages and methods that can be used. You can visit the official documentation for more information about QueryBuilder.

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