SQL将多个列的表简化为更少的列

我有一张如下所示的表格：

PO_ID | PO_TYPE | PO_STAT | MR_ID | MR_TYPE | MR_STAT | IN_ID | IN_TYPE | IN_STAT
  1   |   A1    |   CO    |   1   |   B1    |   DR    |   1   |   C1    |  CO
  2   |   A1    |   CO    |   2   |   B2    |   CO    |   2   |   C1    |  CO

我想把这个表简化成这样：

ID   |  TYPE  | STAT
 1   |  A1    | CO
 2   |  A1    | CO
 1   |  B1    | DR
 2   |  B2    | CO
 1   |  C1    | CO
 1   |  C1    | CO

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怎么可能呢

你可以试试这样的

 select PO_ID as ID,PO_TYPE as TYPE,PO_STAT as STAT from table
    union all
 select MR_ID,MR_TYPE,MR_STAT from table

.... and so on

您可以使用Union all来实现这一点

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除了这个答案。重命名列名。从表中选择采购订单ID作为ID，采购订单类型作为类型，采购订单统计作为统计

SELECT PO_ID AS ID, PO_TYPE AS TYPE, PO_STAT AS STAT FROM TABLE
UNION ALL 
SELECT MR_ID AS ID, MR_TYPE AS TYPE, MR_STAT AS STAT FROM TABLE
UNION ALL
SELECT IN_ID AS ID, IN_TYPE AS TYPE, IN_STAT AS STAT FROM TABLE