Andy,
Well that depends. If you want to see clients that don't have any products, you would just add the other tables in as left joins and add to the where clause in a similar manner. If, on the other hand, you want to see the all of the clients and all the products and which ones the client has, you need to pivot the data. Something like this could work:
select c.*,
(i1.clientId is not null) insProd1,
(i2.clientId is not null) insProd2,
(i3.clientId is not null) insProd3
from Clients c
left join InsuranceProduct1 i1
on c.clientId = i1.clientId
left join InsuranceProduct2 i2
on c.clientId = i2.clientId
left join InsuranceProduct3 i3
on c.clientId = i3.clientId;
And if you only want the clients that are missing at least one product, add a where clause like this to the above query:
where i1.clientId is null
or i2.clientId is null
or i3.clientId is null;
HTH,
Chad