Question

<appSettings>
    <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true"/>
    <add key="inputFilePath" value="~/products.json"/>
    <!--<add key="outputFilePath" value="C:\FormatedProductDetail.txt"/>-->
    <add key="outputFilePath" value="C:\inetpub\ProductSelector\FormatedProductDetail.json"/>
</appSettings>

上面的查询返回一个像这样的输出

select pd.products_name, 
GROUP_CONCAT(pag.customers_group_id SEPARATOR ',') group_id, 
pa.`options_values_price` Retail, 
GROUP_CONCAT(pag.options_values_price SEPARATOR ',') volume_and_designer


from products_attributes pa 

left join products_description pd 
on pa.products_id = pd.products_id and pd.language_id = '1' 

left join products_attributes_groups pag 
on pa.`products_attributes_id`= pag.`products_attributes_id`

where pa.products_id='225'

GROUP BY `pa`.`products_attributes_id` 

ORDER BY `pa`.`products_attributes_id` ASC

我想要实现的是在上表中再添加2个别名，以便根据group_id列将最后一列（volume_and_sdesign）分成两列（即volume，SDesign）。 1对应于音量，2对应于SDesign。

e.g

| products_name | group_id |   Retail |   volume_and_sdesign |
-------------------------------------------------------------
| GOLD          |    1,2   |  15      |       30,35          |
| SILVER        |    2,1   |  16      |       40,45          |
| BRONZE        |    1,2   |  17      |       50,55          |

所以，上面的表格看起来像这样

Gold has group_id (1,2)
so its volume_and_sdesign (30,35) will make new columns 
volume = 30
SDesign = 35

Silver has group_id (2,1)
so its volume_and_sdesign (40,45) will make new columns 
volume = 45
SDesign = 40

 Bronze has group_id (1,2)
so its volume_and_sdesign (50,55) will make new columns 
volume = 50
SDesign = 55

非常感谢任何帮助

Answer 1

您可以在聚合函数（例如case）中使用条件聚合 - max()：

select pd.products_name, 
       group_concat(pag.customers_group_id SEPARATOR ',') as group_id, 
       pa.`options_values_price` as  Retail, 
       group_concat(pag.options_values_price SEPARATOR ',') as volume_and_designer,
       max(case when group_id = 1 then pag.options_values_price end) as volume,
       max(case when group_id = 2 then pag.options_values_price end) as SDesign
from products_attributes pa left join
     products_description pd 
     on pa.products_id = pd.products_id and pd.language_id = '1' left join
     products_attributes_groups pag 
     on pa.`products_attributes_id` = pag.`products_attributes_id`
where pa.products_id='225'
group by `pa`.`products_attributes_id` 
order by `pa`.`products_attributes_id` ASC

Answer 2

这可以使用LEFT，RIGHT和SUBSTRING_INDEX来实现。

试试这个：

select
    pd.products_name, 
    GROUP_CONCAT(pag.customers_group_id SEPARATOR ',') group_id, 
    pa.`options_values_price` Retail, 
    GROUP_CONCAT(pag.options_values_price SEPARATOR ',') volume_and_designer,
    IF(LEFT(group_id,1) = 1, SUBSTRING_INDEX(volume_and_designer, ',', 1), SUBSTRING_INDEX(volume_and_designer, ',', -1)) as volume,
    IF(RIGHT(group_id,1) = 1, SUBSTRING_INDEX(volume_and_designer, ',', 1), SUBSTRING_INDEX(volume_and_designer, ',', -1)) as SDesign
from products_attributes pa 
left join products_description pd 
on pa.products_id = pd.products_id and pd.language_id = '1' 
left join products_attributes_groups pag 
on pa.`products_attributes_id`= pag.`products_attributes_id`
where pa.products_id='225'
GROUP BY `pa`.`products_attributes_id` 
ORDER BY `pa`.`products_attributes_id` ASC

MySql将别名拆分为多个列

2 个答案: