How to Retrieve Default and Character-Specific Settings Using a LEFT JOIN?

Efficiently Retrieving Default and Character-Specific Settings with LEFT JOIN

This example demonstrates how to retrieve default settings and, where applicable, character-specific overrides using a LEFT JOIN. The original query only returned character-specific settings, excluding defaults.

The key to retrieving both is to correctly position the WHERE clause. Instead of filtering after the join, incorporate the character ID filter within the join condition:

SELECT settings.*, character_settings.value
FROM settings
LEFT JOIN character_settings 
ON character_settings.setting_id = settings.id
AND character_settings.character_id = '1';

This revised query performs a LEFT JOIN between the settings and character_settings tables. The ON clause ensures that only matching setting_ids are joined, and further restricts the join to records where character_id is '1'. Crucially, the LEFT JOIN guarantees that all rows from the settings table are included in the result, even if there's no matching row in character_settings.

The resulting dataset will resemble this:

array(
    0 => array('somekey' => 'keyname', 'value' => 'thevalue'), // Default + Character-specific (if exists)
    1 => array('somekey2' => 'keyname2', 'value' => null), // Default only
    2 => array('somekey3' => 'keyname3', 'value' => null)  // Default only
);

Rows with a non-null value indicate both default and character-specific settings. NULL values in the value column signify that only the default setting exists for that particular key.

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