mysql实现分组排序
CREATE TABLE user_orders (orders_id INT UNSIGNED NOT NULL,user_id INT UNSIGNED NOT NULL,
add_time INT UNSIGNED NOT NULL,
PRIMARY KEY(orders_id),
KEY(user_id),
KEY(add_time)
)ENGINE=INNODB DEFAULT CHARSET utf8 COMMENT 'mysql实现分组排序测试表';
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('1','1','1');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('2','1','2');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('3','1','3');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('4','2','1');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('5','2','2');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('6','2','3');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('7','3','1');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('8','3','2');
INSERT INTO `user_orders` (`orders_id`, `user_id`, `add_time`) VALUES('9','3','3');
SELECT orders_id,user_id,add_time,rank FROM (
SELECT@rownum:=@rownum+1 AS rownum,# 行号
IF(@x=uo.user_id,@rank:=@rank+1,@rank:=1) rank,#处理排名，如果@x等于user_id，则表示@x被初始化，将@rank自增1
@x:=uo.user_id, # 初始化@x，@x为中间变量,在rank之后初始化,所以，rank初始化时，@x为null或者是上一个user_id的值
orders_id,user_id,add_time
FROM
user_ordersuo,
(SELECT @rownum:=0,@rank:=0) init # 初始化信息表
ORDER BY user_id ASC, add_time DESC
)result
WHERE rank=2
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