Entiendo. Y si lo haces asi?
Código:
select distinct valor from Tabla
where CLAVE like '%Seccion1' and R='5' and C='2'
and plantilla='Plantilla a' and EXISTS
(select * from Tabla
where CLAVE like '%Seccion1' and R='2' and C='4' and plantilla='Plantilla a' and substring(valor,7,4)='2006')
