When I am Trying to login showing 500 internal server error..

and on error log showing..
`WordPress database error Can't create/write to file '/tmp/#sql_6286_22.MYI' (Errcode: 28) for query SELECT t.*, tt.*, tr.object_id FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN wp_term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ('category', 'post_tag', 'post_format') AND tr.object_id IN (1945) ORDER BY t.name ASC made by require('wp-blog-header.php'), wp, WP->main, WP->query_posts, WP_Query->query, WP_Query->get_posts, update_post_caches, update_object_term_cache, wp_get_object_terms`