Hi,

I have a performance problem on a query.

First table is a Customer table which has millions records in it. Customer table has a column of email address and some other information about customer.

Second table is a CommunicationInfo table which contains just Email addresses.

And What I want in here is; how many times the email address in CommunicationInfo table repeats in Customers table. What could be the the most performer query.

The basic query that I can explain this situation is;

Select ci.Email, count(*) from Customer c left join 
CommunicationInfo ci on c.Email1 = ci.Email or c.Email2 = ci.Email 
Group by ci.Email

But sure, it takes about 5, 6 minutes in execution.

Thanks in Advance.