>Here we are again
>
>

>select individual_ref from contact where individual_ref in (190999,191000,191001,191002)
>

>
>returns
>
>191002
>191002
>
>there are 2 matching records. Thats correct
>
>
>

>select individual_ref from individual where family_ref = 190997
>

>
>returns
>
>190999
>191000
>191001
>191002
>
>again thats correct
>
>So why would
>
>

>select i.individual_ref from individual i where not EXISTS (select c.individual_ref from contact c ) 
>

>
>return no rows ?
>
>I'm expecting
>
>190999
>191000
>191001
>
>any ideas .
>
>Thanks

Because your subquery is not linked to the main query. It should be:

select i.individual_ref from individual i 
where not EXISTS (select 1 from contact c where c.individual_ref = i.Individual_Ref ) 

The way you wrote your query just checks if the Contact table has at least one row. If it's true, it will return 0 records.