mysql中order by 排序用asc和desc不起作用怎么回事

Posted 2023-04-27

一张表，里边有'regdate'字段，用select语句查询后排序用desc和asc不起作用什么原因呢？
select * from test where remark = '学生' group by regdate desc
就这条，当时练习的时候怎么都出不来。现在可以了，纳闷。。

你排序的字段是否都是重复的，你可以以当前字段为排序字段，后面再追加一个次要的排序字段，比如ordery by orderid desc, id asc 参考技术A select * from test where remark = '学生' group by regdate order by ?? desc

需要增加order by 关键字 ??处是你要排序的字段 再后面是 desc降序 asc升序 参考技术B 去专门的论坛或者请教专门的高手看看吧。追加问题不一定能及时解决。本回答被提问者采纳 参考技术C 字段类型是什么。 参考技术D order by 写成了 group by。。。。。

python：mysql之ORDER BY 语句

接下来。装逼开始....

ORDER BY 语句用于对结果集进行排序操作

• ORDER BY 语句可以指定任何字段作为排序条件

• ORDER BY 语句也可以指定多个字段作为排序条件

• ORDER BY 语句也可以指定ASC或DESC关键字设置结果集是升序还是降序

• ORDER BY 语句是跟在SQL语句最后面的

• ORDER BY 语句默认情况下是升序排序，也就是执行ASC

示例1：终端执行SQL语句，查询到结果集后并默认排序为升序

mysql> select * from test_user_copy;+----+--------+-------------+----------+-----------+---------------------+| id | name | mobile | address | country | school |+----+--------+-------------+----------+-----------+---------------------+| 1 | JAVA | 18847474541 | Beijing | China | Beijing University || 2 | Python | 17748484242 | Nanjing | Singapore | Nanjing University || 3 | SQL | 17748484246 | Beijing | China | Beijing University || 4 | R | 17748484141 | Shanghai | Singapore | Shanghai University |+----+--------+-------------+----------+-----------+---------------------+4 rows in set (0.00 sec)
mysql> select * from test_user_copy order by country;+----+--------+-------------+----------+-----------+---------------------+| id | name | mobile | address | country | school |+----+--------+-------------+----------+-----------+---------------------+| 1 | JAVA | 18847474541 | Beijing | China | Beijing University || 3 | SQL | 17748484246 | Beijing | China | Beijing University || 2 | Python | 17748484242 | Nanjing | Singapore | Nanjing University || 4 | R | 17748484141 | Shanghai | Singapore | Shanghai University |+----+--------+-------------+----------+-----------+---------------------+4 rows in set (0.00 sec)

示例2：python执行SQL语句，查询到结果集后并设置排序为降序

import pymysql

class MysqlData: def __init__(self, host="localhost", user="root", password="123456", database="testing", port=3306): # 连接数据库 self.connection = pymysql.connect(host=host, user=user, password=password, database=database, port=port, charset='utf8', cursorclass=pymysql.cursors.DictCursor)
 def modify_data(self, sql, args=None): """ Args: sql: sql语句            args:   接收格式化参数 Returns: """ try: with self.connection: self.connection.ping(reconnect=True) with self.connection.cursor() as cursor: # 执行sql语句 cursor.execute(sql, args=args) # 提交sql语句 self.connection.commit() except pymysql.err.MySQLError as _error: raise _error
 def get_data(self, sql, args=None, is_data=False): """ Args: sql: sql语句 args: 接收格式化参数            is_data:    判断获取多条数据还是单个数据，默认获取单个数据 Returns: """ try: with self.connection: self.connection.ping(reconnect=True) with self.connection.cursor() as cursor: # 执行sql语句 cursor.execute(sql, args=args)
 # 返回查询出的数据信息 return cursor.fetchall() if is_data else cursor.fetchone()
 except pymysql.err.MySQLError as _error: raise _error

if __name__ == '__main__': # 初始化类，创建对象 info = MysqlData()
 # 调用查询多条数据方法 results = info.get_data(""" SELECT * FROM test_user_copy ORDER BY country DESC """, is_data=True)  # 循环列表，获取数据 for i in results: print(i)

{'id': 2, 'name': 'Python', 'mobile': '17748484242', 'address': 'Nanjing', 'country': 'Singapore', 'school': 'Nanjing University'}{'id': 4, 'name': 'R', 'mobile': '17748484141', 'address': 'Shanghai', 'country': 'Singapore', 'school': 'Shanghai University'}{'id': 5, 'name': 'C++', 'mobile': '17748484141', 'address': 'Shenzhen', 'country': 'France', 'school': 'Shanghai University'}{'id': 1, 'name': 'JAVA', 'mobile': '18847474541', 'address': 'Beijing', 'country': 'China', 'school': 'Beijing University'}{'id': 3, 'name': 'SQL', 'mobile': '17748484246', 'address': 'Beijing', 'country': 'China', 'school': 'Beijing University'}
Process finished with exit code 0

从返回的结果集可以看到，country这一列已经做了降序排序...

示例3：python执行SQL语句，查询到结果集后并设置id升序、country为降序

if __name__ == '__main__': # 初始化类，创建对象 info = MysqlData()
 # 调用查询多条数据方法 results = info.get_data(""" SELECT * FROM test_user_copy ORDER BY id DESC, country DESC """, is_data=True)  # 循环列表，获取数据  for i in results:        print(i)

{'id': 5, 'name': 'C++', 'mobile': '17748484141', 'address': 'Shenzhen', 'country': 'France', 'school': 'Shanghai University'}{'id': 4, 'name': 'R', 'mobile': '17748484141', 'address': 'Shanghai', 'country': 'Singapore', 'school': 'Shanghai University'}{'id': 3, 'name': 'SQL', 'mobile': '17748484246', 'address': 'Beijing', 'country': 'China', 'school': 'Beijing University'}{'id': 2, 'name': 'Python', 'mobile': '17748484242', 'address': 'Nanjing', 'country': 'Singapore', 'school': 'Nanjing University'}{'id': 1, 'name': 'JAVA', 'mobile': '18847474541', 'address': 'Beijing', 'country': 'China', 'school': 'Beijing University'}
Process finished with exit code 0

从返回的结果集可以看到，优先生效的是id排序...

至此，mysql中使用 ORDER BY 语句查询数据完成...

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