Mysql 选择在此位置无效(

我已经用CASE编写了一个查询，但是我遇到了（）问题

select SM.subscriber_name as name ,
       SM.accountType as accountType,
       SM.middlename as middleName,
       SM.lastname as lastName,
       SM.title as title,
       SM.email as email,
       SM.company as company,
       SM.email1 as aEmail,
       ,
       SM.zipcode as zipcode,
       SM.phone_no as phoneNumber,
       SM.landlinenumber as landlineNumber,
       SM.login_id as loginId, 
       SD.subscriberType as subscriptionType,
       SD.product_id as productType,
       case SM.state when 'null' then '' as state else STDD.state_name as state end,
       case SM.city when 'null' then '' as city else  CDD.city_name as city end,
       case SM.country when 'null' then '' as country else CD.country_name as country end,
       SD.fulldownloadaccess as fullDownloadAccess,
       SD.emailid_limit as emailLimit,
       SD.acessTime as planTime
from subscriber_master SM , 
     subsciber_details SD,
     city_details CDD,
     state_details STDD, 
     country_details CD
where SM.subscriber_id=16704 and 
      SM.subscriber_id=SD.subscriber_id and 
      SM.country = CD.country_id and
      SM.state = STDD.state_id and
      SM.city = CDD.city_id;

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请帮助我将括号放在哪里。您的查询有几个问题。首先，您的

CASE

表达式写得不正确，表达式必须在任何

AS

部分（参见）之前完成，例如

case SM.state when 'null' then '' as state else STDD.state_name as state end,

应写为

case SM.state when 'null' then '' else STDD.state_name end as state,

此外，如果要检查

NULL

值，而不是字符串值

'NULL'

，则需要将

大小写为：

case when SM.state IS NULL then '' else STDD.state_name end as state

另外，您还有一个额外的
，
（介于
SM.email1作为aEmail，
和
SM.zipcode作为zipcode，
）之间

但是，这些问题都不会在标题中显示消息，是否有一些代码没有显示给我们？
我想说，您有兴趣将空值显示为空值，因此，您需要重新生成查询，如下所示：

  CASE sm.state 
          WHEN 'null' THEN ''  AS state 
          ELSE stdd.state_name AS state 
                                  end, 

改写为：

  CASE  
          WHEN sm.state IS NULL THEN ''  
          ELSE stdd.state_name END AS state, 

所有“NULL”都是一样的。另外，AS应该在案例结束后写入

回顾：刚刚意识到下面的句子应该返回相同的内容，但更简洁易读：

ISNULL(sm.state, '') AS state,

您可以更改如下所示的
case
语句，它将同时检查
null
和空白值

case ISNULL(SM.[state],'') when '' then '' else STDD.state_name end as [state],
       case ISNULL(SM.city,'') when '' then '' else CDD.city_name end as city,
       case ISNULL(SM.country,'') when '' then '' else CD.country_name end as country

您应该使用
join
来提供select语句中不同表之间的where条件。或者，您也可以使用下面修改的查询

select SM.subscriber_name as name ,
       SM.accountType as accountType,
       SM.middlename as middleName,
       SM.lastname as lastName,
       SM.title as title,
       SM.email as email,
       SM.company as company,
       SM.email1 as aEmail,       
       SM.zipcode as zipcode,
       SM.phone_no as phoneNumber,
       SM.landlinenumber as landlineNumber,
       SM.login_id as loginId, 
       SD.subscriberType as subscriptionType,
       SD.product_id as productType,
       case ISNULL(SM.[state],'') when '' then '' else STDD.state_name end as [state],
       case ISNULL(SM.city,'') when '' then '' else CDD.city_name end as city,
       case ISNULL(SM.country,'') when '' then '' else CD.country_name end as country,
       SD.fulldownloadaccess as fullDownloadAccess,
       SD.emailid_limit as emailLimit,
       SD.acessTime as planTime
from subscriber_master SM, 
     subsciber_details SD,
     city_details CDD,
     state_details STDD, 
     country_details CD      
where SM.subscriber_id=16704
 and  SM.subscriber_id=SD.subscriber_id and 
      SM.country = CD.country_id and
      SM.[state] = STDD.state_id and
      SM.city = CDD.city_id;

您使用的是哪个数据库？可能是检查语法-->
SM.email1作为aEmail
在这两个
，
之后。谢谢。您的回答很有帮助