apply_filters_ref_array( ‘posts_groupby’, string $groupby, WP_Query $query )

User Contributed Notes

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   Steven Lin 4 years ago

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   Example migrated from Codex:

   add_filter( 'posts_groupby', 'my_posts_groupby' );
   
   function my_posts_groupby($groupby) {
       global $wpdb;
       $groupby = "{$wpdb->posts}.ID";
       return $groupby;
   }

   The code above will just set the GROUP BY clause whether or not, a taxonomy query or a meta query is present.

   For example, say we have a custom table (for ratings) and we wish to filter the posts using data from this table (only show posts that have a 5 star rating).

   We can use the posts_join filter to join the tables. If there are multiple entries in the ratings table, the join can return multiple results for the same post.

   We can make sure that we only have one row per post (that has all the entries for the ratings) by setting the GROUP BY clause. Remember that in the default query, GROUP BY clause is only set when there is a meta query or taxonomy query involved.