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Overview

The Database library provides a simple abstraction layer for database operations. It supports multiple database engines through adapters.

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DB Class Structure

From system/library/db.php:17: 
namespace Opencart\System\Library;

class DB {
    private object $adaptor;
    
    public function __construct(array $option = []) {
        $required = ['engine', 'hostname', 'username', 'database', 'port'];
        
        foreach ($required as $key) {
            if (empty($option[$key])) {
                throw new \Exception('Error: Database ' . $key . ' required!');
            }
        }
        
        $class = 'Opencart\System\Library\DB\\' . $option['engine'];
        $this->adaptor = new $class($option);
    }
    
    public function query(string $sql) {
        return $this->adaptor->query($sql);
    }
    
    public function escape(string $value): string {
        return $this->adaptor->escape($value);
    }
    
    public function countAffected(): int {
        return $this->adaptor->countAffected();
    }
    
    public function getLastId(): int {
        return $this->adaptor->getLastId();
    }
    
    public function isConnected(): bool {
        return $this->adaptor->isConnected();
    }
}

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Core Methods

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query()

Execute SQL statements: 
$query = $this->db->query("SELECT * FROM `" . DB_PREFIX . "product` WHERE `product_id` = '50'");

// Access results
$row = $query->row;        // Single row as array
$rows = $query->rows;      // All rows as array of arrays
$count = $query->num_rows; // Number of rows returned

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escape()

Prevent SQL injection: 
$name = $this->db->escape($user_input);
$this->db->query("SELECT * FROM product WHERE name = '" . $name . "'");

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countAffected()

Get number of affected rows: 
$this->db->query("UPDATE product SET status = '1' WHERE category_id = '10'");
$affected = $this->db->countAffected(); // Number of updated rows

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getLastId()

Get auto-increment ID from INSERT: 
$this->db->query("INSERT INTO product SET name = 'New Product'");
$product_id = $this->db->getLastId();

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Next Steps

Session Library

Session management

Cache Library

Caching operations