刪除表中多余的重復記錄，重復記錄是根據單個字段（id）來判斷，只留有rowid最小的記錄 

//刪除用戶 根據用戶名，并且不包括最小ID
delete from users where username in (
         --根據用戶名稱排序，大于1
	select username from users group by username having count(username) > 1
 
 ) and Id not in (
        --根據用戶名排序，獲取最小ID
	select min(Id) from users group by username having count(username) > 1
);

轉載請注明出處 AE博客|墨淵 ? SQL 刪除重復記錄，只保留一條記錄