Viewing, adding and editing database content - drupal

Question

I just started using Drupal and I was wondering if there is an easy way of viewing, adding or editing data from my custom database. Are there tutorials/modules which allow me to do these actions?
Sorry for the newbie question, I have no idea what to look for...

Answer 1

This question is perhaps more suitable for the Drupal Answers community.
Connecting a custom database
There is a great tutorial on how to connect Drupal to a separate, custom database, called How to connect to multiple databases within Drupal. In summary, it can be achieved by adding the following code into your settings.php file.
<?php
$databases = array();
$databases['default']['default'] = array(
// Drupal's database credentials go here
);
$databases['custom']['default'] = array(
// Custom database credentials go here
);
?>
Accessing custom database
First, tell Drupal that you're accessing a custom database, by inserting db_set_active('custom'); right before your query. To switch back to Drupal's default database, insert db_set_active();.
To make queries to your database, refer to a list of Database Functions. Although these functions are geared more towards a Drupal's default database, you'll find that certain functions will work on a custom database. For example, for simple SELECT queries, you may want to use the db_query.
db_query usage:
<?php
$uid = 1;
$result = db_query('SELECT n.nid, n.title, n.created
FROM {node} n WHERE n.uid = :uid', array(':uid' => $uid));
// Fetch next row as a stdClass object.
$record = $result->fetchObject();
// Fetch next row as an associative array.
$record = $result->fetchAssoc();
// Fetch data from specific column from next row
// Defaults to first column if not specified as argument
$data = $result->fetchColumn(1); // Grabs the title from the next row
// Retrieve a single value
$result->fetchField();
// Retrieve all records into an indexed array of stdClass objects.
$result->fetchAll();
// Retrieve all records as stdObjects into an associative array
// keyed by the field in the result specified.
// (in this example, the title of the node)
$result->fetchAllAssoc('title');
// Retrieve a 2-column result set as an associative array of field 1 => field 2.
$result->fetchAllKeyed();
// Also good to note that you can specify which two fields to use
// by specifying the column numbers for each field
$result->fetchAllKeyed(0,2); // would be nid => created
$result->fetchAllKeyed(1,0); // would be title => nid
// Retrieve a 1-column result set as one single array.
$result->fetchCol();
// Column number can be specified otherwise defaults to first column
$result->fetchCol($db_column_number);
// Count the number of rows
$result->rowCount();
?>

Answer 2

You were not clear if you need to merely manage the data, or edit the data in Drupal. If managing data is the need, use a front-end. Since you are using Drupal, you must be using PHP. If you are new to accessing databases, you may like to use PHPMyAdmin http://www.phpmyadmin.net. It may be already included with your PHP distribution if you installed PHP with MAMP, or XAMMP or one of the similar packages, but you didn't say.
Viewing, adding and editing database data in Drupal requires reading and understanding the Drupal database API https://www.drupal.org/developing/api/database