Apache Drill上的联合为NULL

Question

我有一个查询，我需要使用Union来获取单行中的所有日期。在联合中钻取不支持NULL。请注意，这是一个示例查询

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Answer 1

select id, nullif(a_supplydate,'')a_supplydate, a_orderdate, nullif(b_supplydate,'')b_supplydate, b_orderdate from    
  (Select ID, Supplydate as A_SupplyDate,OrderDate as A_Orderdate,
           '' as B_SupplyDate,NULL as B_OrderDate 
           from tbl where Category='A'
    union
       Select ID, '' as A_SupplyDate,NULL as A_Orderdate,
           Supplydate as B_SupplyDate,OrderDate as B_OrderDate 
              from tbl where Category='B')A

Answer 2

将您的null设置为适当的数据类型，例如cast(null as bigint)