WordPress - wp_postmeta for specific post id

1SELECT *
2FROM `sp`.`wp_postmeta` where `post_id` = 676902;

1SELECT meta_value
2FROM wp_postmeta
3WHERE post_id = 676902
4AND meta_key = '_edit_last';

1SELECT p.ID, p.post_title, pm.meta_value
2FROM wp_posts p
3INNER JOIN wp_postmeta pm ON p.ID = pm.post_id
4WHERE pm.meta_key = 'view_count'
5AND CAST(pm.meta_value AS UNSIGNED) > 1000
6ORDER BY CAST(pm.meta_value AS UNSIGNED) DESC;

1SELECT
2    post_id,
3    MAX(CASE WHEN meta_key = '_thumbnail_id' THEN meta_value END) AS thumbnail_id,
4    MAX(CASE WHEN meta_key = '_edit_last' THEN meta_value END) AS last_editor,
5    MAX(CASE WHEN meta_key = 'view_count' THEN meta_value END) AS views
6FROM wp_postmeta
7WHERE post_id = 676902
8GROUP BY post_id;

1SELECT
2    post_id,
3    COUNT(*) AS meta_count,
4    GROUP_CONCAT(meta_key ORDER BY meta_key SEPARATOR ', ') AS meta_keys
5FROM wp_postmeta
6WHERE post_id IN (676902, 676903, 676904)
7GROUP BY post_id;

1<?php
2// Get single meta value
3$view_count = get_post_meta(676902, 'view_count', true);
4
5// Get all metadata for a post
6$all_meta = get_post_meta(676902);
7
8// Update or create meta value
9update_post_meta(676902, 'view_count', 1500);
10
11// Add new meta value (allows duplicates)
12add_post_meta(676902, 'custom_field', 'value', false);
13
14// Delete meta value
15delete_post_meta(676902, 'old_field');

1<?php
2// Get posts with specific meta value
3$args = array(
4    'post_type' => 'post',
5    'meta_query' => array(
6        array(
7            'key' => 'view_count',
8            'value' => 1000,
9            'compare' => '>',
10            'type' => 'NUMERIC'
11        )
12    )
13);
14$popular_posts = new WP_Query($args);
15
16// Bulk update meta values
17global $wpdb;
18$wpdb->query($wpdb->prepare(
19    "UPDATE {$wpdb->postmeta}
20     SET meta_value = meta_value + 1
21     WHERE meta_key = %s
22     AND post_id = %d",
23    'view_count',
24    676902
25));

1<?php
2// Register meta box
3function register_custom_meta_box() {
4    add_meta_box(
5        'custom_post_metadata',
6        'Custom Post Metadata',
7        'display_custom_meta_box',
8        'post',
9        'side',
10        'high'
11    );
12}
13add_action('add_meta_boxes', 'register_custom_meta_box');
14
15// Display meta box content
16function display_custom_meta_box($post) {
17    wp_nonce_field('custom_meta_box_nonce', 'meta_box_nonce');
18    $view_count = get_post_meta($post->ID, 'view_count', true);
19    ?>
20    <label for="view_count">View Count:</label>
21    <input type="number" id="view_count" name="view_count"
22           value="<?php echo esc_attr($view_count); ?>" />
23    <?php
24}
25
26// Save meta box data
27function save_custom_meta_box($post_id) {
28    if (!isset($_POST['meta_box_nonce']) ||
29        !wp_verify_nonce($_POST['meta_box_nonce'], 'custom_meta_box_nonce')) {
30        return;
31    }
32
33    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
34        return;
35    }
36
37    if (isset($_POST['view_count'])) {
38        update_post_meta(
39            $post_id,
40            'view_count',
41            intval($_POST['view_count'])
42        );
43    }
44}
45add_action('save_post', 'save_custom_meta_box');

1CREATE INDEX idx_meta_key_value ON wp_postmeta(meta_key, meta_value(50));

1-- Instead of: SELECT * FROM wp_postmeta WHERE post_id = 676902
2-- Use specific columns:
3SELECT meta_key, meta_value
4FROM wp_postmeta
5WHERE post_id = 676902;

1<?php
2// WordPress caches this automatically
3$meta = get_post_meta(676902, 'view_count', true);
4
5// Clear cache when needed
6wp_cache_delete(676902, 'post_meta');
7
8// Or use transients for expensive queries
9$cache_key = 'popular_posts_' . md5(serialize($args));
10$results = get_transient($cache_key);
11
12if (false === $results) {
13    $results = $wpdb->get_results($query);
14    set_transient($cache_key, $results, HOUR_IN_SECONDS);
15}

1<?php
2// Sanitize before saving
3$safe_value = sanitize_text_field($_POST['custom_field']);
4update_post_meta($post_id, 'custom_field', $safe_value);
5
6// Validate and type-cast numeric values
7$view_count = absint($_POST['view_count']);
8update_post_meta($post_id, 'view_count', $view_count);
9
10// Escape on output
11echo esc_html(get_post_meta($post_id, 'custom_field', true));

1<?php
2global $wpdb;
3
4// WRONG - vulnerable to SQL injection
5$results = $wpdb->get_results(
6    "SELECT * FROM {$wpdb->postmeta} WHERE meta_key = '{$_GET['key']}'"
7);
8
9// CORRECT - using prepared statements
10$results = $wpdb->get_results($wpdb->prepare(
11    "SELECT * FROM {$wpdb->postmeta} WHERE meta_key = %s",
12    $_GET['key']
13));

1<?php
2$serialized = get_post_meta(676902, '_wp_attachment_metadata', true);
3$unserialized = maybe_unserialize($serialized);
4
5// Or use WordPress function that handles this automatically
6$meta = get_post_meta(676902, '_wp_attachment_metadata', true);
7// Returns unserialized data automatically

1DELETE pm
2FROM wp_postmeta pm
3LEFT JOIN wp_posts p ON pm.post_id = p.ID
4WHERE p.ID IS NULL;