如果地址丢失，Mysql customer_details显示其他列值

Question

我编写了一个查询来显示客户的客户 ID、客户姓名和联系方式，如果地址缺失，则显示电子邮件 ID，如果地址和电子邮件都丢失，则显示"NA"，我正在根据客户 ID 对结果进行排序，但我没有得到任何输出。

我的表结构

customer_id VARCHAR(10)
customer_name VARCHAR(20)
address VARCHAR(20)
phoneno BIGINT
email_id VARCHAR(20)

select customer_id,customer_name,phone_no,email_id from customers ,
where
if(address isnull) and if(email_id isnull) then 
"NA"
if(address isnull) then 
email_id
order by customer_id;

触发查询

Program Outpput
customer_id customer_name   phone_no    email_id    address
C001    Amith   9843123467  [e-mail] Bangalore
C002    Anand   9487256231  NULL    NA
C003    Bala    9442478962  [e-mail]  Chennai
C004    Gowri   9487267845  [e-mail] Coimbatore
C005    Priya   9843134523  [e-mail] Cochin
C006    Prem    9528431343  [e-mail]  Coimbatore
C007    Rahul   9513428433  [e-mail] [e-mail]
C008    John    9982843342  [e-mail]  Chennai
C009    Abdul   9843065418  [e-mail] [e-mail]
Expected Output
customer_id customer_name   contact_details
C001    Amith   Bangalore
C002    Anand   NA
C003    Bala    Chennai
C004    Gowri   Coimbatore
C005    Priya   Cochin
C006    Prem    Coimbatore
C007    Rahul   [e-mail]
C008    John    Chennai
C009    Abdul   [e-mail]

Answer 1

SELECT customer_id, customer_name, COALESCE(address, email_id, 'NA')
AS contact_details
FROM customers;

Answer 2

select customer_id,customer_name,
case
when email_id is null and address is null then 'NA'
when address is null then email_id
else address
end as 'CONTACT_DETAILS'
FROM customers
order by customer_id;

Answer 3

SELECT customer_id, customer_name, coalesce(address, email_id, 'NA') AS contact_details FROM customers ORDER BY customer_id ASC;

Answer 4

select customer_id,customer_name,
case
when(phone_no is null and address is null) then
email_id 
when(phone_no is null) then 
address
else    
phone_no    
end contact_details from customer order by customer_id asc;