test=# SELECT * FROM
(
SELECT ROW_NUMBER() OVER (PARTITION By name ORDER BY create_time DESC) AS rownum, name, order_cnt FROM order_tab
) T
WHERE T.rownum = 1;
 rownum | name | order_cnt
--------+------+-----------
      1 | 李四 |         4
      1 | 张山 |         5
(2 rows)