獲取最短日期作爲條件

Question

我有一個表包含所有電話號碼的發票，每個號碼有幾個發票，我想只顯示精確數字的第一張發票，但我真的不知道如何只獲得第一張發票，這是我的查詢

SELECT 
    b.contrno 
    a.AR_INVDATE 
    FROM P_STG_TABS.IVM_INVOICE_RECORD a 

    INNER JOIN P_EDW_TMP.invoice b 
    ON b.contrno=a.contrno 

    WHERE a.AR_INVDATE< (SELECT AR_INVDATE FROM P_STG_TABS.IVM_INVOICE_RECORD WHERE contrno=b.contrno ) 

Answer 1

使用ROW_NUMBER()：

SELECT 
    t.contrno, 
    t.AR_INVDATE 
FROM 
(
    SELECT 
     b.contrno, 
     a.AR_INVDATE, 
     ROW_NUMBER() OVER (PARTITION BY b.contrno ORDER BY a.AR_INVDATE) rn 
    FROM P_STG_TABS.IVM_INVOICE_RECORD a 
    INNER JOIN P_EDW_TMP.invoice b 
     ON b.contrno = a.contrno 
) t 
WHERE t.rn = 1; 

如果你擔心聯繫，要顯示所有的聯繫，那麼你就可以無論RANK或DENSE_RANK更換ROW_NUMBER。

Answer 2

如果我正確理解，再一個方法是使用group by與min(a.AR_INVDATE)：

SELECT 
b.contrno, 
min(a.AR_INVDATE) 
FROM P_STG_TABS.IVM_INVOICE_RECORD a 
INNER JOIN P_EDW_TMP.invoice b 
ON b.contrno=a.contrno 
group by b.contrno 

Answer 3

Teradata的支持QUALIFY子句來過濾OLAP-函數的結果（類似於HAVINGGROUP BY之後），從而大大簡化添Biegeleisens的回答是：

SELECT * 
FROM P_STG_TABS.IVM_INVOICE_RECORD a 
INNER JOIN P_EDW_TMP.invoice b 
    ON b.contrno = a.contrno 
QUALIFY 
    ROW_NUMBER() 
    OVER (PARTITION BY b.contrno 
     ORDER BY a.AR_INVDATE) = 1 

另外，你可以將ROW_NUMBER在連接前（可能是取決於附加條件更有效）：

SELECT * 
FROM 
(SELECT * 
    FROM P_STG_TABS.IVM_INVOICE_RECORD a 
    QUALIFY 
     ROW_NUMBER() 
     OVER (PARTITION BY b.contrno 
      ORDER BY a.AR_INVDATE) = 1 
) AS a 
INNER JOIN P_EDW_TMP.invoice b 
    ON b.contrno = a.contrno