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mysql有没有开窗函数_mysql实现开窗函数

發(fā)布時間：2023/12/16 数据库 26 豆豆

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mysql實現(xiàn)開窗函數(shù)

開窗分析函數(shù)簡單來講就是相似partition by aaa, bbb order by ccc這樣的形式mysql

在使用mysql的過程當中遇到過這樣的需求，須要求出一段時間內(nèi)每一個item的最大值及對應(yīng)的那一條記錄。最大值很容易使用group by item求出來，可是求出那一條對應(yīng)的全部字段及值卻很差實現(xiàn)。通過查資料及探索發(fā)現(xiàn)mysql也能夠?qū)崿F(xiàn)，思路是人為構(gòu)造一個字段來標記順序，這樣不只能實現(xiàn)最大，還能實現(xiàn)TOP N。記錄下簡單示例：sql

準備數(shù)據(jù)

# 建表

CREATE TABLE `policy_summary` (

`id` int(11) NOT NULL AUTO_INCREMENT,

`policy_name` varchar(18) COLLATE utf8_bin DEFAULT NULL,

`publish_time` datetime DEFAULT NULL,

`platform_id` int(11) DEFAULT NULL,

PRIMARY KEY (`id`)

)

# 插入數(shù)據(jù)

INSERT INTO `policy_summary` VALUES ('1', 'test0', '2019-04-01 15:11:00', '2');

INSERT INTO `policy_summary` VALUES ('2', 'test9', '2019-04-01 19:11:00', '2');

INSERT INTO `policy_summary` VALUES ('3', 'test8', '2019-04-01 19:11:00', '2');

INSERT INTO `policy_summary` VALUES ('4', 'test7', '2019-04-01 18:11:00', '2');

INSERT INTO `policy_summary` VALUES ('5', 'test1', '2019-04-01 15:11:00', '2');

INSERT INTO `policy_summary` VALUES ('6', 'test2', '2019-04-01 15:11:00', '2');

INSERT INTO `policy_summary` VALUES ('7', 'test3', '2019-04-01 16:11:00', '2');

INSERT INTO `policy_summary` VALUES ('8', 'test4', '2019-04-01 16:11:00', '2');

INSERT INTO `policy_summary` VALUES ('9', 'test5', '2019-04-01 16:11:00', '2');

INSERT INTO `policy_summary` VALUES ('10', 'test6', '2019-04-01 17:11:00', '2');

INSERT INTO `policy_summary` VALUES ('11', 'fengyu', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('12', '新建政策1111111', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('13', '1218測試', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('14', 'xxx', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('15', 'ccc', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('16', '測試114', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('17', '測試mmm', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('18', 'kkkkkkk', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('19', 'kkkkkkk明明', '2019-04-02 19:17:00', '8');

INSERT INTO `policy_summary` VALUES ('20', 'ceshi111', '2019-04-02 19:17:00', '8');

# 查看

mysql> select * from policy_summary;

+----+-----------------+---------------------+-------------+

+----+-----------------+---------------------+-------------+

| 1 | test0 | 2019-04-01 15:11:00 | 2 |

| 2 | test9 | 2019-04-01 19:11:00 | 2 |

| 3 | test8 | 2019-04-01 19:11:00 | 2 |

| 4 | test7 | 2019-04-01 18:11:00 | 2 |

| 5 | test1 | 2019-04-01 15:11:00 | 2 |

| 6 | test2 | 2019-04-01 15:11:00 | 2 |

| 7 | test3 | 2019-04-01 16:11:00 | 2 |

| 8 | test4 | 2019-04-01 16:11:00 | 2 |

| 9 | test5 | 2019-04-01 16:11:00 | 2 |

| 10 | test6 | 2019-04-01 17:11:00 | 2 |

| 11 | fengyu | 2019-04-02 19:17:00 | 8 |

| 12 | 新建政策1111111 | 2019-04-02 19:17:00 | 8 |

| 13 | 1218測試 | 2019-04-02 19:17:00 | 8 |

| 14 | xxx | 2019-04-02 19:17:00 | 8 |

| 15 | ccc | 2019-04-02 19:17:00 | 8 |

| 16 | 測試114 | 2019-04-02 19:17:00 | 8 |

| 17 | 測試mmm | 2019-04-02 19:17:00 | 8 |

| 18 | kkkkkkk | 2019-04-02 19:17:00 | 8 |

| 19 | kkkkkkk明明 | 2019-04-02 19:17:00 | 8 |

| 20 | ceshi111 | 2019-04-02 19:17:00 | 8 |

+----+-----------------+---------------------+-------------+

根據(jù)platform_id,publish_time分組并根據(jù)policy_name排序

SELECT

a.platform_id,

a.publish_time,

a.policy_name,

a.id,

IF (

@str1 = a.platform_id

AND @str2 = a.publish_time,

@rank := @rank + 1,

@rank := 1

) AS rank_no,

@str1 := a.platform_id,

@str2 := a.publish_time

FROM

(

SELECT

platform_id,

publish_time,

policy_name,

FROM

policy_summary

ORDER BY

platform_id,

publish_time,

policy_name ASC

) a,

(

SELECT

@str1 := 0,

@str2 := NULL,

@rank := 0

) tmp

# 查詢結(jié)果

+-------------+---------------------+-----------------+----+---------+------------------------+-------------------------+

+-------------+---------------------+-----------------+----+---------+------------------------+-------------------------+

| 2 | 2019-04-01 15:11:00 | test0 | 1 | 1 | 2 | 2019-04-01 15:11:00 |

| 2 | 2019-04-01 15:11:00 | test1 | 5 | 2 | 2 | 2019-04-01 15:11:00 |

| 2 | 2019-04-01 15:11:00 | test2 | 6 | 3 | 2 | 2019-04-01 15:11:00 |

| 2 | 2019-04-01 16:11:00 | test3 | 7 | 1 | 2 | 2019-04-01 16:11:00 |

| 2 | 2019-04-01 16:11:00 | test4 | 8 | 2 | 2 | 2019-04-01 16:11:00 |

| 2 | 2019-04-01 16:11:00 | test5 | 9 | 3 | 2 | 2019-04-01 16:11:00 |

| 2 | 2019-04-01 17:11:00 | test6 | 10 | 1 | 2 | 2019-04-01 17:11:00 |

| 2 | 2019-04-01 18:11:00 | test7 | 4 | 1 | 2 | 2019-04-01 18:11:00 |

| 2 | 2019-04-01 19:11:00 | test8 | 3 | 1 | 2 | 2019-04-01 19:11:00 |

| 2 | 2019-04-01 19:11:00 | test9 | 2 | 2 | 2 | 2019-04-01 19:11:00 |

| 8 | 2019-04-02 19:17:00 | 1218測試 | 13 | 1 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | ccc | 15 | 2 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | ceshi111 | 20 | 3 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | fengyu | 11 | 4 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | kkkkkkk | 18 | 5 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | kkkkkkk明明 | 19 | 6 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | xxx | 14 | 7 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | 新建政策1111111 | 12 | 8 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | 測試114 | 16 | 9 | 8 | 2019-04-02 19:17:00 |

| 8 | 2019-04-02 19:17:00 | 測試mmm | 17 | 10 | 8 | 2019-04-02 19:17:00 |

+-------------+---------------------+-----------------+----+---------+------------------------+-------------------------+

這樣rank_no就是那個標志排序的字段，若是要求最大policy_name的記錄就只須要加一個過濾條件rank_no <= 1便可函數(shù)

SELECT

t.platform_id,

t.publish_time,

t.policy_name,

t.rank_no,

t.id

FROM

(

SELECT

a.id,

a.platform_id,

a.publish_time,

a.policy_name,

IF (

@str1 = a.platform_id

AND @str2 = a.publish_time,

@rank := @rank + 1,

@rank := 1

) AS rank_no,

@str1 := a.platform_id,

@str2 := a.publish_time

FROM

(

SELECT

id,

platform_id,

publish_time,

policy_name

FROM

policy_summary

ORDER BY

platform_id,

publish_time,

policy_name ASC

) a,

(

SELECT

@str1 := 0,

@str2 := NULL,

@rank := 0

) tmp

) t

WHERE

t.rank_no <= 1

參考

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