MySql 将别名拆分为多个列

Question

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

上面的查询返回这样的输出

| 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          |

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volume，2对应SDesign。

例如

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

所以，上表看起来是这样的

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

任何帮助将不胜感激

Answer 1

您可以使用条件聚合——即 case 在聚合函数中，例如 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