Question

如果贝娄条件为真，我需要从THEN列获取Mortgage_Type的值。

Mortgage_Type和Category与另一个表和设备相同表

使用Item_No加入表。我需要找到Mortgage_Type 每个物品。如果Category是main和Equipment，我有20+ Mortgage_Types 为null然后应显示相关的Mortgage_Type

 when SUM (Mortgage_Type)is not null and SUM (Equipment)is null and
    sum(Category) ='M' THEN “value from Mortgage_Type column”

Answer 1

只需输入列名：

CASE 
   WHEN (Mortgage_Type)is not null and (Equipment)is null and (Category) ='M' 
    THEN Mortgage_Type
    ELSE <other value>
END

Answer 2

你可以这样做：

CASE  WHEN Col1 is not null AND Col2 is null AND Col3 = 'M' THEN 'value'
      ...
      ELSE 0 END as Column

或

CASE Col1 WHEN <value> THEN '' WHEN <value> THEN '' ELSE <your value>END

Answer 3

如果要为类别的每个值输出不同的名称，则应使用SQL case语句，例如：

*

CASE 
       WHEN cat=1 THEN 'category one'
       WHEN cat=2 THEN 'category two'
       WHEN cat=3 THEN 'category tree'
       ELSE 'other category'
END

*

您可以在表格中准备一个带有连接的简单SQL语句，如下所述：

select A.Mortgage_Type,B.Item_No from table_A A, table_B B where A.Item_No = B.Item_No
and A.Mortgage_Type is not null and B.Equipment is null and A.Category ='M'

我真的不明白你的“B.equipment is null”条件，是强制性的吗？如果您没有任何Morgage_type，您想提供默认值吗？

Answer 4

如果您的mortgage_type列不在加入中使用的表中，那么

- 使用此

CASE 
   WHEN (Mortgage_Type)is not null and (Equipment)is null and (Category) ='M' 
    THEN (SELECT Mortgage_Type FROM <table_name> WHERE <condition>)
    ELSE <........>
END

如果在连接中存在mortgate_type column't表，那么

- 使用此

CASE 
   WHEN (Mortgage_Type)is not null and (Equipment)is null and (Category) ='M' 
    THEN mortgage_type
    ELSE <........>
END

Answer 5

假设我们的两个表是Mortgage_details（Item_No，Mortgage_type，category），而Equipment_Details（Item_No，Equipment）假设您拥有列的数据类型。

为了选择所需的Mortgage_Type，您可以在下面的查询中包含一个case语句：

select Item_No,
case when Mortgage_Type is not null and Equipment is null and Category ='M' 
THEN Mortgage_Type
Else Mortgage_Type 
End as Relevent_Mortgage_type,
from Mortgage_details m
join Equipment_details e
on m.Item_no = e.Item_no;

而不是Mortgage_Type in Else对于不满足上述条件的行，您可以拥有任何值。

案例表达式，如何从Then子句中的列中获取值

5 个答案: