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小編給大家分享一下MySQL8.0窗口函數實例詳解，希望大家閱讀完這篇文章后大所收獲，下面讓我們一起去探討吧！
MySQL8.0之前，做數據排名統計等相當痛苦，因為沒有像Oracle、SQL SERVER 、PostgreSQL等其他數據庫那樣的窗口函數。但隨著MySQL8.0中新增了窗口函數之后，針對這類統計就再也不是事了，
1、準備工作
創建表及測試數據
mysql> use testdb;
Database changed
/* 創建表 */
mysql> create table tb_score(id int primary key auto_increment,stu_no varchar(10),course varchar(50),score decimal(4,1)，key idx_stuNo_course(stu_no,course));
Query OK, 0 rows affected (0.03 sec)
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| tb_score |
+------------------+
/* 新增一批測試數據 */
mysql> insert into tb_score(stu_no,course,score)values('2020001','mysql',90),('2020001','C++',85),('2020003','English',100),('2020002','mysql',50),('2020002','C++',70),('2020002','English',99);
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> insert into tb_score(stu_no,course,score)values('2020003','mysql',78),('2020003','C++',81),('2020003','English',80),('2020004','mysql',80),('2020004','C++',60),('2020004','English',100);
Query OK, 6 rows affected (0.01 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> insert into tb_score(stu_no,course,score)values('2020005','mysql',98),('2020005','C++',96),('2020005','English',70),('2020006','mysql',60),('2020006','C++',90),('2020006','English',70);
Query OK, 6 rows affected (0.01 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> insert into tb_score(stu_no,course,score)values('2020007','mysql',50),('2020007','C++',66),('2020007','English',76),('2020008','mysql',90),('2020008','C++',69),('2020008','English',86);
Query OK, 6 rows affected (0.01 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> insert into tb_score(stu_no,course,score)values('2020009','mysql',70),('2020009','C++',66),('2020009','English',86),('2020010','mysql',75),('2020010','C++',76),('2020010','English',81);
Query OK, 6 rows affected (0.01 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> insert into tb_score(stu_no,course,score)values('2020011','mysql',90),('2020012','C++',85),('2020011','English',84),('2020012','English',75),('2020013','C++',96),('2020013','English',88);
Query OK, 6 rows affected (0.01 sec)
Records: 6 Duplicates: 0 Warnings: 02、統計每門課程分數的排名
根據每門課程的分數從高到低進行排名，此時，會出現分數相同時怎么處理的問題，下面就根據不同的窗口函數來處理不同場景的需求
ROW_NUMBER
由結果可以看出，分數相同時按照學號順序進行排名
mysql> select stu_no,course,score, row_number()over(partition by course order by score desc ) rn -> from tb_score; +---------+---------+-------+----+ | stu_no | course | score | rn | +---------+---------+-------+----+ | 2020005 | C++ | 96.0 | 1 | | 2020013 | C++ | 96.0 | 2 | | 2020006 | C++ | 90.0 | 3 | | 2020001 | C++ | 85.0 | 4 | | 2020012 | C++ | 85.0 | 5 | | 2020003 | C++ | 81.0 | 6 | | 2020010 | C++ | 76.0 | 7 | | 2020002 | C++ | 70.0 | 8 | | 2020008 | C++ | 69.0 | 9 | | 2020007 | C++ | 66.0 | 10 | | 2020009 | C++ | 66.0 | 11 | | 2020004 | C++ | 60.0 | 12 | | 2020003 | English | 100.0 | 1 | | 2020004 | English | 100.0 | 2 | | 2020002 | English | 99.0 | 3 | | 2020013 | English | 88.0 | 4 | | 2020008 | English | 86.0 | 5 | | 2020009 | English | 86.0 | 6 | | 2020011 | English | 84.0 | 7 | | 2020010 | English | 81.0 | 8 | | 2020003 | English | 80.0 | 9 | | 2020007 | English | 76.0 | 10 | | 2020012 | English | 75.0 | 11 | | 2020005 | English | 70.0 | 12 | | 2020006 | English | 70.0 | 13 | | 2020005 | mysql | 98.0 | 1 | | 2020001 | mysql | 90.0 | 2 | | 2020008 | mysql | 90.0 | 3 | | 2020011 | mysql | 90.0 | 4 | | 2020004 | mysql | 80.0 | 5 | | 2020003 | mysql | 78.0 | 6 | | 2020010 | mysql | 75.0 | 7 | | 2020009 | mysql | 70.0 | 8 | | 2020006 | mysql | 60.0 | 9 | | 2020002 | mysql | 50.0 | 10 | | 2020007 | mysql | 50.0 | 11 | +---------+---------+-------+----+ 36 rows in set (0.00 sec)mysql> select stu_no,course,score, row_number()over(partition by course order by score desc ) rn -> from tb_score; +---------+---------+-------+----+ | stu_no | course | score | rn | +---------+---------+-------+----+ | 2020005 | C++ | 96.0 | 1 | | 2020013 | C++ | 96.0 | 2 | | 2020006 | C++ | 90.0 | 3 | | 2020001 | C++ | 85.0 | 4 | | 2020012 | C++ | 85.0 | 5 | | 2020003 | C++ | 81.0 | 6 | | 2020010 | C++ | 76.0 | 7 | | 2020002 | C++ | 70.0 | 8 | | 2020008 | C++ | 69.0 | 9 | | 2020007 | C++ | 66.0 | 10 | | 2020009 | C++ | 66.0 | 11 | | 2020004 | C++ | 60.0 | 12 | | 2020003 | English | 100.0 | 1 | | 2020004 | English | 100.0 | 2 | | 2020002 | English | 99.0 | 3 | | 2020013 | English | 88.0 | 4 | | 2020008 | English | 86.0 | 5 | | 2020009 | English | 86.0 | 6 | | 2020011 | English | 84.0 | 7 | | 2020010 | English | 81.0 | 8 | | 2020003 | English | 80.0 | 9 | | 2020007 | English | 76.0 | 10 | | 2020012 | English | 75.0 | 11 | | 2020005 | English | 70.0 | 12 | | 2020006 | English | 70.0 | 13 | | 2020005 | mysql | 98.0 | 1 | | 2020001 | mysql | 90.0 | 2 | | 2020008 | mysql | 90.0 | 3 | | 2020011 | mysql | 90.0 | 4 | | 2020004 | mysql | 80.0 | 5 | | 2020003 | mysql | 78.0 | 6 | | 2020010 | mysql | 75.0 | 7 | | 2020009 | mysql | 70.0 | 8 | | 2020006 | mysql | 60.0 | 9 | | 2020002 | mysql | 50.0 | 10 | | 2020007 | mysql | 50.0 | 11 | +---------+---------+-------+----+ 36 rows in set (0.00 sec)
DENSE_RANK
為了讓分數相同時排名也相同，則可以使用DENSE_RANK函數，結果如下：
mysql> select stu_no,course,score, DENSE_RANK()over(partition by course order by score desc ) rn -> from tb_score ; +---------+---------+-------+----+ | stu_no | course | score | rn | +---------+---------+-------+----+ | 2020005 | C++ | 96.0 | 1 | | 2020013 | C++ | 96.0 | 1 | | 2020006 | C++ | 90.0 | 2 | | 2020001 | C++ | 85.0 | 3 | | 2020012 | C++ | 85.0 | 3 | | 2020003 | C++ | 81.0 | 4 | | 2020010 | C++ | 76.0 | 5 | | 2020002 | C++ | 70.0 | 6 | | 2020008 | C++ | 69.0 | 7 | | 2020007 | C++ | 66.0 | 8 | | 2020009 | C++ | 66.0 | 8 | | 2020004 | C++ | 60.0 | 9 | | 2020003 | English | 100.0 | 1 | | 2020004 | English | 100.0 | 1 | | 2020002 | English | 99.0 | 2 | | 2020013 | English | 88.0 | 3 | | 2020008 | English | 86.0 | 4 | | 2020009 | English | 86.0 | 4 | | 2020011 | English | 84.0 | 5 | | 2020010 | English | 81.0 | 6 | | 2020003 | English | 80.0 | 7 | | 2020007 | English | 76.0 | 8 | | 2020012 | English | 75.0 | 9 | | 2020005 | English | 70.0 | 10 | | 2020006 | English | 70.0 | 10 | | 2020005 | mysql | 98.0 | 1 | | 2020001 | mysql | 90.0 | 2 | | 2020008 | mysql | 90.0 | 2 | | 2020011 | mysql | 90.0 | 2 | | 2020004 | mysql | 80.0 | 3 | | 2020003 | mysql | 78.0 | 4 | | 2020010 | mysql | 75.0 | 5 | | 2020009 | mysql | 70.0 | 6 | | 2020006 | mysql | 60.0 | 7 | | 2020002 | mysql | 50.0 | 8 | | 2020007 | mysql | 50.0 | 8 | +---------+---------+-------+----+ 36 rows in set (0.00 sec)
RANK
DENSE_RANK的結果是分數相同時排名相同了，但是下一個名次是緊接著上一個名次的，如果2個并列的第1之后，下一個我想是第3名，則可以使用RANK函數實現
mysql> select stu_no,course,score, rank()over(partition by course order by score desc ) rn -> from tb_score; +---------+---------+-------+----+ | stu_no | course | score | rn | +---------+---------+-------+----+ | 2020005 | C++ | 96.0 | 1 | | 2020013 | C++ | 96.0 | 1 | | 2020006 | C++ | 90.0 | 3 | | 2020001 | C++ | 85.0 | 4 | | 2020012 | C++ | 85.0 | 4 | | 2020003 | C++ | 81.0 | 6 | | 2020010 | C++ | 76.0 | 7 | | 2020002 | C++ | 70.0 | 8 | | 2020008 | C++ | 69.0 | 9 | | 2020007 | C++ | 66.0 | 10 | | 2020009 | C++ | 66.0 | 10 | | 2020004 | C++ | 60.0 | 12 | | 2020003 | English | 100.0 | 1 | | 2020004 | English | 100.0 | 1 | | 2020002 | English | 99.0 | 3 | | 2020013 | English | 88.0 | 4 | | 2020008 | English | 86.0 | 5 | | 2020009 | English | 86.0 | 5 | | 2020011 | English | 84.0 | 7 | | 2020010 | English | 81.0 | 8 | | 2020003 | English | 80.0 | 9 | | 2020007 | English | 76.0 | 10 | | 2020012 | English | 75.0 | 11 | | 2020005 | English | 70.0 | 12 | | 2020006 | English | 70.0 | 12 | | 2020005 | mysql | 98.0 | 1 | | 2020001 | mysql | 90.0 | 2 | | 2020008 | mysql | 90.0 | 2 | | 2020011 | mysql | 90.0 | 2 | | 2020004 | mysql | 80.0 | 5 | | 2020003 | mysql | 78.0 | 6 | | 2020010 | mysql | 75.0 | 7 | | 2020009 | mysql | 70.0 | 8 | | 2020006 | mysql | 60.0 | 9 | | 2020002 | mysql | 50.0 | 10 | | 2020007 | mysql | 50.0 | 10 | +---------+---------+-------+----+ 36 rows in set (0.01 sec)
這樣就實現了各種排序需求。
NTILE
NTILE函數的作用是對每個分組排名后，再將對應分組分成N個小組，例如
mysql> select stu_no,course,score, rank()over(partition by course order by score desc )rn,NTILE(2)over(partition by course order by score desc ) rn_group from tb_score; +---------+---------+-------+----+----------+ | stu_no | course | score | rn | rn_group | +---------+---------+-------+----+----------+ | 2020005 | C++ | 96.0 | 1 | 1 | | 2020013 | C++ | 96.0 | 1 | 1 | | 2020006 | C++ | 90.0 | 3 | 1 | | 2020001 | C++ | 85.0 | 4 | 1 | | 2020012 | C++ | 85.0 | 4 | 1 | | 2020003 | C++ | 81.0 | 6 | 1 | | 2020010 | C++ | 76.0 | 7 | 2 | | 2020002 | C++ | 70.0 | 8 | 2 | | 2020008 | C++ | 69.0 | 9 | 2 | | 2020007 | C++ | 66.0 | 10 | 2 | | 2020009 | C++ | 66.0 | 10 | 2 | | 2020004 | C++ | 60.0 | 12 | 2 | | 2020003 | English | 100.0 | 1 | 1 | | 2020004 | English | 100.0 | 1 | 1 | | 2020002 | English | 99.0 | 3 | 1 | | 2020013 | English | 88.0 | 4 | 1 | | 2020008 | English | 86.0 | 5 | 1 | | 2020009 | English | 86.0 | 5 | 1 | | 2020011 | English | 84.0 | 7 | 1 | | 2020010 | English | 81.0 | 8 | 2 | | 2020003 | English | 80.0 | 9 | 2 | | 2020007 | English | 76.0 | 10 | 2 | | 2020012 | English | 75.0 | 11 | 2 | | 2020005 | English | 70.0 | 12 | 2 | | 2020006 | English | 70.0 | 12 | 2 | | 2020005 | mysql | 98.0 | 1 | 1 | | 2020001 | mysql | 90.0 | 2 | 1 | | 2020008 | mysql | 90.0 | 2 | 1 | | 2020011 | mysql | 90.0 | 2 | 1 | | 2020004 | mysql | 80.0 | 5 | 1 | | 2020003 | mysql | 78.0 | 6 | 1 | | 2020010 | mysql | 75.0 | 7 | 2 | | 2020009 | mysql | 70.0 | 8 | 2 | | 2020006 | mysql | 60.0 | 9 | 2 | | 2020002 | mysql | 50.0 | 10 | 2 | | 2020007 | mysql | 50.0 | 10 | 2 | +---------+---------+-------+----+----------+ 36 rows in set (0.01 sec)
3、窗口函數小結
MySQL中還有許多其他的窗口函數，本文列舉一些，大家可以自行測試
| 類別 | 函數 | 說明 |
| 排序 | ROW_NUMBER | 為表中的每一行分配一個序號，可以指定分組（也可以不指定）及排序字段 |
| DENSE_RANK | 根據排序字段為每個分組中的每一行分配一個序號。 排名值相同時，序號相同，序號中沒有間隙（1,1,2,3這種） | |
| RANK | 根據排序字段為每個分組中的每一行分配一個序號。 排名值相同時，序號相同，但序號中存在間隙（1,1,3,4這種） | |
| NTILE | 根據排序字段為每個分組中根據指定字段的排序再分成對應的組 | |
| 分布 | PERCENT_RANK | 計算各分組或結果集中行的百分數等級 |
| CUME_DIST | 計算某個值在一組有序的數據中累計的分布 | |
| 前后 | LEAD | 返回分組中當前行之后的第N行的值。如果不存在對應行，則返回NULL。比如N=1時，第一名對應的值是第二名的，最后一名結果是NULL |
| LAG | 返回分組中當前行之前的第N行的值。如果不存在對應行，則返回NULL。比如N=1時，第一名對應的值是是NUL，最后一名結果是倒數第2的值 | |
| 首尾中 | FIRST_VALUE | 返回每個分組中第一名對應的字段（或表達式）的值，例如本文中可以是第一名的分數、學號等任意字段的值 |
| LAST_VALUE | 返回每個分組中最后一名對應的字段（或表達式）的值，例如本文中可以是最后一名的分數、學號等任意字段的值 | |
| NTH_VALUE | 返回每個分組中排名第N的對應字段（或表達式）的值，但小于N的行對應的值是NULL |
MySQL中主要的窗口函數先總結這么多，建議還是得動手實踐一番。另外，MySQL5.7及之前版本的排序方式的實現很多人已總結，也建議實操一番。
看完了這篇文章，相信你對MySQL8.0窗口函數實例詳解有了一定的了解，想了解更多相關知識，歡迎關注億速云行業資訊頻道，感謝各位的閱讀！
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