solr delta import not working properly

I have 8 tables in my solr data-config files and all are joined since i need data from all of them. But out of those 8 tables i have three tables that have common fields ,which i can use to link.But the issues is that the common fields in the three table that i have are such that they are repeating values. eg:-

First table(businessmasters) has 2 columns

Business_id(pk)    Business_name       Mod1(on update timestamp)
       1                        ABC           
       2                        XYZ 
       3                        KOT


Second table(search_tag) has 3 columns 
     Search_tag_id(pk)   Business_id  Search_tag_name           Mod2(on update timestamp)
         1                      1           hair
         2                      1           trimming                     
         3                      2            massage
         4                      1            facial
         5                      2            makeup

Now i want to join the two tables and i do that on the basis of Business_id.But since iam joining on Business_id which is a non key in second table i just write that business_id is a key(because if i cant use Search_tag_id as its not common in both tables and if i take Search_tag_id as pk and join the tables on Business_id solr gives an error during delta import "deltaQuery has no column to resolve to declared primary key"). But when i say that Business_id is pk and join tables on the basis of that it works fine and delta import works.

But the issue comes when i try to change the Business_id in second table eg i want to change the Business_id of Search_tag_id 3 to 1 and i run delta import.The update adds the search tag to Business_id 1 but also doesn't remove the search tag from Business_ID 2.The value of search tags in Business_id 2 remains there ,where as it should go away if iam changing Business_id from 2 to 1.Since now Business_id is not linked to any search tag. Iam not able to figure out how to resolve this issue.This is how i write it in data-config file.

 <entity name="businessmasters" pk="business_id" query="SELECT Business_id,
  Business_name,Mod1 from businessmasters"
  deltaImportQuery="SELECT Business_id,Business_name,Mod1 from businessmasters where         
  business_id='${dih.delta.business_id}"
  deltaQuery="select business_id from businessmasters where modified > '${dih.last_index_time}'">

   <field column="business_id" name="id"/>   
   <field column="business_name" name="business_name" indexed="true" stored="true" />
   <field column="Mod1" name="Mod1" indexed="true" stored="true" />


   <entity name="search_tag"  pk="business_id" query="SELECT Search_tag_id,Search_tag_name from            
   search_tag where business_id='${businessmasters.business_id}'"
   deltaQuery="select business_id from search_tag where Mod2  > '${dih.last_index_time}'"
   parentDeltaQuery="select business_id from businessmasters where     
   business_id=${search_tag.business_id}">

     <field column="business_id " name="id" />
     <field column="Search_tag_id" name="Search_tag_id" indexed="true" stored="true" />
     <field column="Search_tag_name  " name="Search_tag_name  " indexed="true" stored="true" />
     <field column="Mod2" name="Mod2" indexed="true" stored="true" />
     </entity>


     </entity>

Thanks in advance iam new to solr and iam stuck on this issue.