Oracle中的Union null

Question

我正在嘗試在oracle中合並2個查詢，這些行具有相同的值，但需要一個字段。

例如：

SELECT NAME, AGE, EMAIL, DATE FROM table_a WHERE NAME = 'JOAO' AND FLAG = '0'
UNION
SELECT NAME, AGE, EMAIL, DATE FROM table_a WHERE NAME = 'JOAO' AND FLAG = '1'

結果：

NAME   AGE   EMAIL      DATE   
JOAO   23    a@a.com    20150414
JOAO   23    a@a.com    null

我如何將這些行分組？ 我正在尋找可以給我類似結果的東西：

NAME   AGE   EMAIL      DATE   
JOAO   23    a@a.com    20150414

謝謝你（抱歉我的英語..）

Answer 1

如果您只是想忽略NULL值：

  SELECT NAME, AGE, EMAIL, DATE 
    FROM table_a 
   WHERE NAME = 'JOAO' 
     AND FLAG in ( '0', '1' )
     and date is not null
  /

或者如果您想保留空值，但要遵循可用的非空值：

  with w_data as (
        SELECT NAME, AGE, EMAIL, DATE ,
               row_number() over ( partition by name
                             order by date desc nulls last ) rnum
          FROM table_a 
         WHERE NAME = 'JOAO' 
           AND FLAG in ( '0', '1' )
     )
  select name, age, email, date
    from w_data
   where rnum = 1
  /

[edit]回應評論：

如果您想保留聯合，那很好，聯合和OR大多可以互換（在這種情況下）：

  SELECT NAME, AGE, EMAIL, DATE 
    FROM table_a 
   WHERE NAME = 'JOAO' 
     AND FLAG = '0'
     and date is not null
     union
  SELECT NAME, AGE, EMAIL, DATE 
    FROM table_a 
   WHERE NAME = 'JOAO' 
     AND FLAG = '1'
     and date is not null
  /

甚至：

  select * from (
  SELECT NAME, AGE, EMAIL, DATE 
    FROM table_a 
   WHERE NAME = 'JOAO' 
     AND FLAG = '0'
   union
  SELECT NAME, AGE, EMAIL, DATE 
    FROM table_a 
   WHERE NAME = 'JOAO' 
     AND FLAG = '1'
  )
  where date is not null
  /

如果您只想將NULL條件放在1個位置；）相同的邏輯可以應用於我上面使用row_number（）分析編寫的第二個查詢...

  with w_data as (
     SELECT NAME, AGE, EMAIL, DATE 
       FROM table_a 
      WHERE NAME = 'JOAO' 
        AND FLAG = '0'
      union
     SELECT NAME, AGE, EMAIL, DATE 
       FROM table_a 
      WHERE NAME = 'JOAO' 
        AND FLAG = '1'
     ),
     w_sub as ( 
        select name, age, email, date,
              row_number() over ( partition by name
                             order by date desc nulls last ) rnum
          from w_data
       )
  select name, age, email, date
    from w_sub
   where rnum = 1
  /

Answer 2

在這種情況下，您可以在“ WHERE”子句中更改您的條件

WHERE NAME = 'JOAO' AND FLAG = '0'

至

WHERE NAME = 'JOAO' AND FLAG IN('0','1')

因此，您的選擇將在“ FLAG”列中顯示所有值為“ 0”或“ 1”的寄存器。

Answer 3

您可以使用COALESCE（）。 http://docs.oracle.com/cd/B28359_01/server.111/b28286/functions023.htm#SQLRF00617/ms190349.aspx

該查詢應適用於每個名稱，並應合並其他行。

SELECT 
    NAME1 AS NAME,
    COALESCE(AGE1, AGE2) AS AGE,
    COALESCE(EMAIL1, EMAIL2) AS EMAIL,
    COALESCE(DATE1, DATE2) AS DATE
FROM(
    SELECT 
        t1.NAME AS NAME1, 
        t1.AGE AS AGE1, 
        t1.EMAIL AS EMAIL1, 
        t1.DATE AS DATE1,
        t2.NAME AS NAME2, 
        t2.AGE AS AGE2, 
        t2.EMAIL AS EMAIL2, 
        t2.DATE AS DATE2 
    FROM table_a AS t1
    INNER JOIN table_a AS t2
    ON t2.FLAG = 1 AND t1.FLAG = 0 AND t1.NAME = t2.NAME
) AS t3;