postgresql - 将单行更改为多行

Question

我有一个名为payment_info的表，其中包含以下记录。

paymentid | customercode | previousbalance | paymentamount | remainingbalance
-----------------------------------------------------------------------------
PID0001   |    CUST024   |    10000        |     2500      |   7500
PID0002   |    CUST031   |    8500         |     3500      |   5000
PID0003   |    CUST005   |    12000        |     1500      |   10500

然后我想要的是创建上表的每行 3 行。我希望我的结果看起来像这样。

Payment Group | Payment Line Item | Payment ID | Customer Code |     Type            | Amount    
--------------------------------------------------------------------------------------------------
   1          |         1         |  PID0001   |   CUST024     | PREVIOUS BALANCE    | 10000.00    
   1          |         2         |            |               | PAYMENT AMOUNT      | 2500.00    
   1          |         3         |            |               | REMAINING BALANCE   | 7500.00    

   2          |         1         |  PID0002   |   CUST031     | PREVIOUS BALANCE    | 8500.00    
   2          |         2         |            |               | PAYMENT AMOUNT      | 3500.00    
   2          |         3         |            |               | REMAINING BALANCE   | 5000.00    

   3          |         1         |  PID0003   |   CUST005     | PREVIOUS BALANCE    | 12000.00    
   3          |         2         |            |               | PAYMENT AMOUNT      | 1500.00    
   3          |         3         |            |               | REMAINING BALANCE   | 10500.00    

这是我开始的查询。但它没有返回与上面相同的结果。

select row_number() over() as id,paymentid,customercode,'PREVIOUS BALANCE' as type,previousbalance from payment_info
union 
select row_number() over() as id,'','','PAYMENT AMOUNT' as type,paymentamount from payment_info
union 
select row_number() over() as id,'','','REMAINING BALANCE' as type,remainingbalance from payment_info

还有其他方法可以不使用 UNION 关键字吗？因为在真实的表中，我将使用 30 多个列，查询数千条记录。

我也不知道如何从付款组（每个付款 ID）和付款行项目（每个组）创建自动生成的号码（ID）。

谢谢

Answer 1

带有空格（空文本）的版本 该unnest函数可以为您执行此操作。如果你想要空文本那么你可以使用这个

SELECT ROW_NUMBER() OVER (ORDER BY paymentid) AS "group",  
unnest(array[1, 2, 3]) AS "line item",  
unnest(array[paymentid, '', '']) AS "paymentid",  
unnest(array[customercode, '', '']) AS "customercode",  
unnest(array['PREVIOUS BALANCE', 'PAYMENT AMOUNT', 'REMAINING BALANCE']) AS "type",  
unnest(array[previousbalance, paymentamount, remainingbalance]) AS "amount"  
FROM payment_info  
ORDER BY 1, 2 ;  

为了得到这个

 group | line item | paymentid | customercode |       type        | amount 
-------+-----------+-----------+--------------+-------------------+--------
     1 |         1 | PID0001   | CUST024      | PREVIOUS BALANCE  |  10000
     1 |         2 |           |              | PAYMENT AMOUNT    |   2500
     1 |         3 |           |              | REMAINING BALANCE |   7500
     2 |         1 | PID0002   | CUST031      | PREVIOUS BALANCE  |   8500
     2 |         2 |           |              | PAYMENT AMOUNT    |   3500
     2 |         3 |           |              | REMAINING BALANCE |   5000
     3 |         1 | PID0003   | CUST005      | PREVIOUS BALANCE  |  12000
     3 |         2 |           |              | PAYMENT AMOUNT    |   1500
     3 |         3 |           |              | REMAINING BALANCE |  10500

例如，如果您想要在空文本列中拥有点或其他文本或箭头，您可以使用 轻松完成此操作unnest。

您可以单独控制 4 个空文本值。

SELECT ROW_NUMBER() OVER (ORDER BY paymentid) AS "group",  
unnest(array[1, 2, 3]) AS "line item",  
unnest(array[paymentid, '      a', '      c']) AS "paymentid",  
unnest(array[customercode, '      b', '      d']) AS "customercode",  
unnest(array['PREVIOUS BALANCE', 'PAYMENT AMOUNT', 'REMAINING BALANCE']) AS "type",  
unnest(array[previousbalance, paymentamount, remainingbalance]) AS "amount"  
FROM payment_info   
ORDER BY 1, 2 ;  

生成

 group | line item | paymentid | customercode |       type        | amount 
-------+-----------+-----------+--------------+-------------------+--------
     1 |         1 | PID0001   | CUST024      | PREVIOUS BALANCE  |  10000
     1 |         2 |       a   |       b      | PAYMENT AMOUNT    |   2500
     1 |         3 |       c   |       d      | REMAINING BALANCE |   7500
     2 |         1 | PID0002   | CUST031      | PREVIOUS BALANCE  |   8500
     2 |         2 |       a   |       b      | PAYMENT AMOUNT    |   3500
     2 |         3 |       c   |       d      | REMAINING BALANCE |   5000
     3 |         1 | PID0003   | CUST005      | PREVIOUS BALANCE  |  12000
     3 |         2 |       a   |       b      | PAYMENT AMOUNT    |   1500
     3 |         3 |       c   |       d      | REMAINING BALANCE |  10500

你知道，这是一个非常灵活的解决方案。