mysql：从一列创建多个列

我现在搜索了很长时间来解决这个难题，希望你们中的一些人能帮助我

我有一个mysql表，如下所示：

**id | role     |**  
--------------------
   1 | staff    |  
   1 | member   |  
   1 | paying   |  
   2 | staff    |  
   2 | admin    |  

我有大约35种不同类型的数据。 我想要的是为角色中的每种类型的数据创建一个列，所以我将以这样的内容结束

**id | staff | member | paying | admin |**  
------------------------------------------
   1 | staff | member | paying | null  |  
   2 | staff | null   | null   | admin |  

如果这有帮助的话，我已经成功地使用CASE生成了行，但是我现在的问题是，我得到了多个具有相同id的行，并且我需要将它们组合成一个。到目前为止，我已经尝试使用group by，但它不起作用

我用这个做柱头

create table ahbtest2 as (
  select
    ahbtest1.*,
    case when f_name = "newsletter" then f_name end as f_newsletter,
    case when f_name = "staff" then f_name end as f_staff,
    case when f_name = "Musician" then f_name end as f_musician,
    case when f_name = "No_membership" then f_name end as f_no_membership,
    case when f_name = "Beirut" then f_name end as f_beirut,
    case when f_name = "VISA" then f_name end as f_visa,
    case when f_name = "3wc" then f_name end as f_3wc,
    case when f_name = "Intl_media" then f_name end as f_intl_media,
    case when f_name = "VIP" then f_name end as f_vip,
    case when f_name = "Music_industry" then f_name end as f_music_industry,
    case when f_name = "senegal" then f_name end as f_senegal,
    case when f_name = "Music_Freedom_Day" then f_name end as f_music_freedom_day,
    case when f_name = "Scholar/student" then f_name end as f_scholar_student,
    case when f_name = "Anniversary_booklet" then f_name end as f_anniversary_booklet,
    case when f_name = "Music_industry" then f_name end as f_music_industry,
    case when f_name = "Old_membership" then f_name end as f_old_membership,
    case when f_name = "2wc" then f_name end as f_2wc,
    case when f_name = "Advisory_Board" then f_name end as f_advisory_board,
    case when f_name = "Danish_media" then f_name end as f_danish_media,
    case when f_name = "Business_contacts" then f_name end as f_business_contacts,
    case when f_name = "Latest_Report" then f_name end as f_latest_report,
    case when f_name = "Press_Alert" then f_name end as f_press_alert,
    case when f_name = "Funding/sponsor" then f_name end as f_funding_sponsor,
    case when f_name = "Diverse/Contacts" then f_name end as f_diverse_contacts,
    case when f_name = "Honorary_membership" then f_name end as f_honorary_membership,
    case when f_name = "Supporting_Membership" then f_name end as f_supporting_membership,
    case when f_name = "GA_2008" then f_name end as f_ga_2008,
    case when f_name = "Stringer" then f_name end as f_stringer,
    case when f_name = "Seminar" then f_name end as f_seminar,
    case when f_name = "Ambassador" then f_name end as f_ambassador,
    case when f_name = "1wc" then f_name end as f_1wc,
    case when f_name = "Evaluation Contacts" then f_name end as f_evaluation_contacts,
    case when f_name = "OIC_APPEAL" then f_name end as f_oic_appeal,
    case when f_name = "Paying membership" then f_name end as f_paying_membership,
    case when f_name = "Executive committee" then f_name end as f_executive_committee,
    case when f_name = "Institutional membership" then f_name end as f_institutional_membership
  from ahbtest1

);

在尝试按id合并行时，这个

select id, name, group_concat(fname)
  from table
  group by id,

---

这在MySQL级别可能会很长，但仍然有可能：

select id, staff, member, ccc from roles
left join (select id, role as staff from roles where role='staff') staff using (id)
left join (select id, role as member from roles where role='member') member using (id)
left join (select id, role as paying from roles where role='paying') paying using (id)
group by id

---

当然，您可以扩展此查询以包括所有可能的值。

关键字到google:pivot表…，然后忽略您发现的内容，而只是在应用程序级别处理显示逻辑…；-）