firebase - 如何检查电子邮件已经存在于firebase颤振中的多个表中

Question

我怎么写：

 if (email and password that be entered exist in **User** table in realtime  firebase){}
 else if (email and password that be entered exist in **UserPart** table in realtime firebase){} 
 else if (email and password that be entered exist in **UserSpon** table in firebase){}
 else {show "there is no account related to this enter information}

在颤振应用中

标签： firebaseflutterdartfirebase-realtime-database