Question

我试图在不使用UNION ALL语句的情况下重新创建此查询，我尝试过标量子查询和模型子句似乎没有做我想要的。我的经理不想使用Union All，但我真的不知道替代方案是什么

任何帮助都会很棒

SELECT null AS UDA_ID,
       'Style-Level Attributes' AS UDA_DESC,
       null AS DISPLAY_TYPE,
       null AS REQUIRED_IND,
       null AS ITEM,
       null AS UDA_TEXT,
       null AS UDA_DATE,
       null AS UDA_VALUE
FROM   DUAL
UNION ALL                 
select a.UDA_ID,
       a.UDA_DESC,
       a.DISPLAY_TYPE,
       a.REQUIRED_IND,
       b.ITEM,
       b.UDA_TEXT,
       b.UDA_DATE,
       b.UDA_VALUE              
from   DAL.P_UDA a,
       FFEDEV.FFE_ITEM_UDA b                
where  a.UDA_ID = b.UDA_ID (+)                
AND    a.REQUIRED_IND IS NOT NULL       
AND    b.ITEM_PARENT IS NULL      
UNION ALL
SELECT null AS UDA_ID,
       'Additional Attributes' AS UDA_DESC,
       null AS DISPLAY_TYPE,
       null AS REQUIRED_IND,
       null AS ITEM,
       null AS UDA_TEXT,
       null AS UDA_DATE,
       null AS UDA_VALUE
FROM   DUAL
UNION ALL                
select a.UDA_ID,
       a.UDA_DESC,
       a.DISPLAY_TYPE,
       a.REQUIRED_IND,
       b.ITEM,
       b.UDA_TEXT,
       b.UDA_DATE,
       b.UDA_VALUE         
from   DAL.P_UDA a,
       FFEDEV.FFE_ITEM_UDA b                
where  a.UDA_ID = b.UDA_ID (+)                
AND    a.REQUIRED_IND IS NULL      
AND    b.ITEM_PARENT IS NULL

Answer 1

我注意到在您的查询中，唯一真正的功能差异在于两个WHERE子句。在UNION ALL的前半部分，条件有：

WHERE a.REQUIRED_IND IS NOT NULL

而下半场有：

WHERE a.REQUIRED_IND IS NULL

您可以使用CASE表达式生成包含属性类型的计算列。为清楚起见，这里是CASE表达式：

CASE WHEN a.REQUIRED_IND IS NOT NULL
    THEN 'Style-Level Attributes'
    ELSE 'Additional Attributes'
END AS UDA_DESC

这是完整的查询：

SELECT CASE WHEN a.REQUIRED_IND IS NOT NULL THEN 'Style-Level Attributes' ELSE 'Additional Attributes' END AS AttrType,
    a.UDA_ID, a.UDA_DESC, a.DISPLAY_TYPE, a.REQUIRED_IND, b.ITEM, b.UDA_TEXT, b.UDA_DATE, b.UDA_VALUE
FROM DAL.P_UDA a
LEFT OUTER JOIN FFEDEV.FFE_ITEM_UDA b
    ON a.UDA_ID = b.UDA_ID
WHERE b.ITEM_PARENT IS NULL
ORDER BY AttrType

此查询中唯一的主要潜在挫折是您丢失了两个空标题行。但是，出于报告目的，应该没有问题。如果你的老板坚持那些空标题行，那么告诉他们它们是合成数据，并且将它们添加到结果集的唯一方法是执行UNION。

Oracle SQL中UNION ALL的替代方法

1 个答案: