DELETE FROM titles_test 
WHERE id NOT IN (
    SELECT id
    FROM 
    (  
		SELECT 
        id,
        ROW_NUMBER() OVER(PARTITION BY emp_no ORDER BY id) AS g_rank
        FROM titles_test
    ) AS rank_table
    WHERE g_rank = 1)

我的方法比很多人使用的min()方法稍微复杂一点,使用了OVER()函数