>>Hi,
>>
>>I am running into a problem where the error message is:
>>

>>Only one expression can be specified in the select list when the
>>subquery is not introduced with EXISTS
>>

>>
>>The SQL Select is as follows:
>>

>>select Table1.Field1 from Table1 where Tabel1.Field1 in (select Table2.Field1, Table2.Field2 from Table2 where 
>>Table2.Field2 in (select Table3.Field2 from Table3))
>>

>>
>>That is, in the above SQL Select there are two IN clauses.
>>
>>Does the error mean that I have to change the second IN with EXISTS? Or both IN have to be change to EXISTS?
>>
>>TIA
>
>
>In your example EXISTS() should perform much faster than IN(). So if the tables are large you might consider:
>
>

>select Table1.Field1 from Table1 
>    where EXISTS(select null from table2 join table3 on table2.field2 = table3.field2 and table2.field1 = table1.field1)
>

>
>Exists will stop looking once it found a match, and the inner join of table2 and table3 automatically filters records that exist in both tables.

I didn't know that Exists is faster than IN(). My tables are not very large. I am testing on the tables of about 3000 rows. I believe that for the largest customer, the tables will not be much larger than 15000 rows.
But I will try your approach. I am always more concerned about making a mistake in the syntax than the speed of execution. 1 second vs 10 seconds - for my customers - does not make a huge difference. But if I can make the code more efficient, why not.
Thank you very much.