Sql server I'；我试图在SQL中运行一个查询，我想知道为什么ADDRESS\u LINE\u 2超过ADDRESS\u LINE\u 1并显示空值

如果将字符串与空值串联，则结果为空

使用

coalesce

或

isnull

确保没有空值：

SELECT    
   EMPLOYEE.EMPLOYEE_FNAME + EMPLOYEE.EMPLOYEE_LNAME +    
         EMPLOYEE.EMPLOYEE_PRIMARY_NUMBER + EMPLOYEE.EMPLOYEE_EMAIL AS EMPLOYEE, 
  ADDRESS.ADDRESS_LINE_1 + ADDRESS.ADDRESS_LINE_2 + ADDRESS.CITY_PROVINCE +   
         ADDRESS.STATE_ABBREVIATION + ADDRESS.POSTAL_CODE AS ADDRESS
FROM         
   EMPLOYEE 
INNER JOIN
  ADDRESS ON EMPLOYEE.ADDRESS_ID = ADDRESS.ADDRESS_ID

---

如果将字符串与空值串联，则结果为空

使用

coalesce

或

isnull

确保没有空值：

SELECT    
   EMPLOYEE.EMPLOYEE_FNAME + EMPLOYEE.EMPLOYEE_LNAME +    
         EMPLOYEE.EMPLOYEE_PRIMARY_NUMBER + EMPLOYEE.EMPLOYEE_EMAIL AS EMPLOYEE, 
  ADDRESS.ADDRESS_LINE_1 + ADDRESS.ADDRESS_LINE_2 + ADDRESS.CITY_PROVINCE +   
         ADDRESS.STATE_ABBREVIATION + ADDRESS.POSTAL_CODE AS ADDRESS
FROM         
   EMPLOYEE 
INNER JOIN
  ADDRESS ON EMPLOYEE.ADDRESS_ID = ADDRESS.ADDRESS_ID

---

您需要确保没有数据是空的

ADDRESS.ADDRESS_LINE_1 + COALESCE(ADDRESS.ADDRESS_LINE_2, '')

---

您需要确保没有数据是空的

ADDRESS.ADDRESS_LINE_1 + COALESCE(ADDRESS.ADDRESS_LINE_2, '')

---

您可以使用以下命令覆盖空连接的默认选项：

isnull(ADDRESS.ADDRESS_LINE_1, '') 
+ isnull(....

---

您可以使用以下命令覆盖空连接的默认选项：

isnull(ADDRESS.ADDRESS_LINE_1, '') 
+ isnull(....

---

如果地址\行\ 1为空怎么办？应该是ISNULL（ADDRESS_LINE_1“”）@roman M：是的，您可以在任何可能为null的字段上使用它。如果ADDRESS_LINE_1为null怎么办？应该是ISNULL（ADDRESS_LINE_1'）@roman M：是的，你会在任何可能为null的字段上使用它。这是一个非常糟糕的主意！此功能将从SQL Server的未来版本中删除这是一个非常糟糕的主意！此功能将从SQL Server的未来版本中删除