You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'CASE 
                    WHEN a.adm_post_name = '' or a.adm_post_name IS NUL...' at line 13: 
            SELECT 
                b.cid, 
                b.id,
                b.title, 
                b.alias, 
                b.`image`,
                b.content,
                b.view, 
                b.new_tdgy,
                b.new_ndgy, 
                b.created_day, 
                b.canonical_url
                CASE 
                    WHEN a.adm_post_name = '' or a.adm_post_name IS NULL 
                    THEN a.adm_name 
                    ELSE a.adm_post_name 
                END as fullname, 
                a.adm_id  as id_admin, 
                b.sapo, 
                cm.name, 
                b.meta_title, 
                b.meta_des,
                b.meta_key,  
                b.bv_index 
            FROM tbl_baiviet as b 
                JOIN admin_user as a ON b.uid = a.adm_id 
                JOIN tbl_chuyenmuc cm ON cm.id = b.cid 
            WHERE b.id = '1406' AND b.status = 1 AND b.admin_approve = 1 AND b.created_day <= '2024-09-20 00:22:10'