如何將一對多關系聚合到 postgres 數據庫中的新列中

Question

我有這個查詢

select cre.id ,string_agg(ae.name, ', ') as agents
from call_report_entity cre 
join report_agents_entity rae on cre.id = rae."reportId" 
join agent_entity ae on rae."agentId" = ae.id 
group by cre .id
order by cre.id desc

結果：

但我需要將結果匯總為：

我怎樣才能達到這個結果？

Answer 1

對於每個 id 固定的最大代理數，您可以使用row_number和條件聚合 pivot：

select id,
    max(name) filter(where rn = 1) agent_1,
    max(name) filter(where rn = 2) agent_2,
    max(name) filter(where rn = 3) agent_3
from (
    select cre.id, ae.name,
        row_number() over(partition by cre.id order by ae.name) rn
    from call_report_entity cre 
    join report_agents_entity rae on cre.id = rae."reportId" 
    join agent_entity ae on rae."agentId" = ae.id
) t
group by id
order by id desc