Mysql转置和分组

Question

我想做一个transpose / groupby。我解释一下我的情况。

我有一张看起来像这样的表

p_qualifier                                          | p_value
-----------------------------------------------------|------------
|mooClassification/1.0/class-4.spherecorrectionlist  |+0.75
|mooClassification/1.0/class-4.spherecorrectionlist  |+1.00
|mooClassification/1.0/class-4.spherecorrectionlist  |+1.25
|mooClassification/1.0/class-4.spherecorrectionlist  |+1.50
|mooClassification/1.0/class-4.spherecorrectionlist  |+1.75

我希望通过查询获得（但我不知道它是否可能）这样的事情

p_qualifier                                          | p_value
-----------------------------------------------------|---------------------------------
|mooClassification/1.0/class-4.spherecorrectionlist  |+0.75; +1.00; +1.25; +1.50; +1,75

感谢您的帮助。

Answer 1

您正在寻找：

SELECT p_qualifier, GROUP_CONCAT(p_value SEPARATOR '; ')
FROM testtable GROUP BY p_qualifier

Answer 2

您可以使用GROUP_CONCAT：

SELECT p_qualifier, GROUP_CONCAT(p_value ORDER BY p_value ASC SEPARATOR '; ') AS `p_value`
FROM table
GROUP BY p_qualifier

它会将列p_qualifier （按相同的行）分组，GROUP_CONCAT会将整个GROUP的结果集连接起来SEPARATOR

Answer 3

如果您想对p_value进行排序。然后在ORDER BY内使用GROUP_CONCAT子句。

查询

SELECT `p_qualifier`,
GROUP_CONCAT(`p_value`
ORDER BY  CAST((RIGHT(`p_value`, LENGTH(`p_value`) - 1)) AS FLOAT) SEPARATOR '; ')  
FROM `your_table_name`
GROUP BY `p_qualifier`;  

希望p_value是varchar。