How Can I Efficiently Retrieve Default and Character-Specific Settings Using a Left Join?

Left Join using WHERE clause: Get default and role-specific settings

The application query needs to retrieve the default settings from the 'settings' table and capture the character-specific settings from the 'character_settings' table if present. However, the current query only returns settings with role ID 1, and the default setting is missing.

The initial query attempts to use the WHERE clause to filter settings where role IDs exist:

<code class="language-sql">SELECT `settings`.*, `character_settings`.`value`
FROM (`settings`)
LEFT JOIN `character_settings` 
ON `character_settings`.`setting_id` = `settings`.`id`
WHERE `character_settings`.`character_id` = '1'</code>

However, this will filter out rows with mismatched left joins, thus removing the desired default.

Solution:

To fix this, relocate the WHERE clause to only join rows where matching role settings exist:

<code class="language-sql">SELECT `settings`.*, `character_settings`.`value`
FROM `settings`
LEFT JOIN `character_settings` 
ON `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1'</code>

The query now collects default settings and role-specific settings if present. A mixed output array structure with default and role values ​​can be created as follows:

<code class="language-php">$result = array();
foreach ($result_set as $row) {
    $result[$row['key']] = $row['value'];
}</code>

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