Find duplicates from different tables

Question

I need to write a  sql query to   find out in which table
 holds the duplicate data.
Duplicate : AAA company should be present(mapped) only once with XXX Partner. If it is repeated then would be considered
 as duplicate
Please help in  writing this query
Table A                                            
Table B                                            
Table C 
company  Partners                    company  Partners                                   
company  Partners     
AAA        XXX                                AAA     
XXX                                                  
AAA      XXX
BBB       YYY                                  BBB     
YYY                                                   
BBB     YYY
AAA       XXXX (duplicate Data)
Expected o/p :
table A contains duplicate data , or Table B contains Duplicate Data ETc...

Answer 1

Chelseasadhu, I do not think AAA is duplicating as the partners are different XXX and XXXX. 
Could you please clarify how are you finding its a duplicate value? Just the Company duplicate is your criteria?
You may try something below:
create Table TableA(Company varchar(100), Partners varchar(100))
Insert into TableA Select 'AAA','XXX'
Insert into TableA Select 'BBB','XXX'
Insert into TableA Select 'AAA','XXXX'
create Table TableB(Company varchar(100), Partners varchar(100))
Insert into TableB Select 'AAA','XXX'
Insert into TableB Select 'BBB','XXX'
--Insert into TableB Select 'BBB','XXXCC'
create Table TableC(Company varchar(100), Partners varchar(100))
Insert into TableC Select 'AAA','XXX'
Insert into TableC Select 'BBB','XXX'
Declare @DuplicateTableA int =0,@DuplicateTableB int=0,@DuplicateTableC int=0
Set @DuplicateTableA=(Select Case when exists(Select COUNT(1) From TableA Group by Company having COUNT(1)>1) then 1 else 0 end)
Set @DuplicateTableB=(Select Case when exists(Select COUNT(1) From TableB Group by Company having COUNT(1)>1) then 1 else 0 end)
Set @DuplicateTableC=(Select Case when exists(Select COUNT(1) From TableC Group by Company having COUNT(1)>1) then 1 else 0 end)
/* Once you have the existence info, its easy for you to do the display at your application layer*/
Declare @DisplayText Varchar(MAX) =''
Set @DisplayText = (Select Case when @DuplicateTableA = 1 then 'TableA contains duplicate data' else '' end)
Set @DisplayText = @DisplayText+(Select Case when Len(@DisplayText)=0 then '' else ' ' End + Case when @DuplicateTableB = 1 then 'TableB contains duplicate data' else '' end)
Set @DisplayText = @DisplayText+(Select Case when Len(@DisplayText)=0 then '' else ' ' End + Case when @DuplicateTableC = 1 then 'TableC contains duplicate data' else '' end)
Select @DisplayText
Drop table TableA,TableB,TableC