不适用于 mysql 中计算列的函数分组

Question

我正在尝试使用聚合案例来创建数据透视表 table。但是，对于我创建的表示行号的列，它显示错误

Code: 1056. Can't group on 'rn'.

与此同时，如果我手动执行相同的工作（通过将 id 列添加到我的 table 它工作正常）。

代码如下：

CREATE TABLE employee (name varchar(128), occupation varchar(128));
INSERT INTO employee VALUES
('Sandra','Gydytoja'),
('Julija','Aktorė'),
('Marija','Aktorė'),
('Martyna','Vadybininkė'),
('Aistė','Mokytoja'),
('Kristina','Mokytoja'),
('Virginija','Mokytoja'),
('Jurga','Aktorė'),
('Justina','Gydytoja'),
('Mia','Vadybininkė');

SELECT ROW_NUMBER() OVER (PARTITION BY occupation ORDER BY name asc) AS rn,
MAX(case when occupation = "Gydytoja" then name end) AS Gydytoja,
MAX(case when occupation = "Aktorė" then name end) AS Aktorė,
MAX(case when occupation = "Vadybininkė" then name end) AS Vadybininkė,
MAX(case when occupation = "Mokytoja" then name end) AS Mokytoja
FROM employee
GROUP BY rn;

在此先感谢您的帮助！

Answer 1

您需要一个子查询来先填充 rn，然后您就可以使用它了：

SELECT rn,
MAX(case when occupation = "Gydytoja" then name end) AS Gydytoja,
MAX(case when occupation = "Aktorė" then name end) AS Aktorė,
MAX(case when occupation = "Vadybininkė" then name end) AS Vadybininkė,
MAX(case when occupation = "Mokytoja" then name end) AS Mokytoja
from ( 
select * , ROW_NUMBER() OVER (PARTITION BY occupation ORDER BY name asc) AS rn
FROM employee
) t 
GROUP BY rn;

rn | Gydytoja | Aktorė | Vadybininkė | Mokytoja 
-: | :------- | :------ | :----------- | :--------
 1 | Justina  | Julija  | Martyna      | Aistė   
 2 | Sandra   | Jurga   | Mia          | Kristina 
 3 | null     | Marija  | null         | Virginija

db<>fiddle here

不适用于 mysql 中计算列的函数分组

Does not work group by function with calculated column in mysql

mysql

group-by

aggregate

case