我試圖在SQL中運行查詢，我想知道爲什麼ADDRESS_LINE_2結束了ADDRESS_LINE_1並顯示爲null

Question

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 

Answer 1

如果您連接字符串和空值，則結果爲空。

使用​​3210或isnull，以確保你沒有一個空值：

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

Answer 2

您需要確保沒有數據是空

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

Answer 3

您可以覆蓋默認選項用於與這個空級聯：

SET CONCAT_NULL_YIELDS_NULL OFF