Salesforce SOQL查询:如何使用SELECT with WHERE条件

对于给定的SOQL查询,尝试优化SOQL查询。我有两个问题

从salesforce获取给定用户帐户的userID

SELECT id From User WHERE Username = 'test@testmail.com'

SELECT Id,Headline__c,Description__c
FROM Incident__c
WHERE Id IN (SELECT Incident__c FROM Node_Affected__c 
        WHERE (Incident__r.Account__c = '034524000000uzurX')
        AND Incident__r.Indicator__c = false)

现在我想将它优化为一个查询,这样就不必从外部系统进行两个api调用。所以我试着

SELECT Id,Headline__c,Description__c
FROM Incident__c
WHERE Id IN (SELECT Incident__c FROM Node_Affected__c 
        WHERE (Incident__r.Account__c = null OR Incident__r.Account__c IN (SELECT id From User WHERE Username = 'test@testmail.com'))
        AND Incident__r.Indicator__c = false)

MALFORMED_QUERY: 
Incident__r.Account__c IN (SELECT id From User WHERE Username = 'test@testmail.com'))
                                          ^
ERROR at Row:5:Column:87
Nesting of semi join sub-selects is not supported

有没有更好的方法来解决这类问题?提前感谢:)