On May 25, 2009, at 4:56 AM, marco santillan wrote:
Hola a todos:
Tengo la siguiente inquietud. En una consulta com la siguiente:
select campo1,
campo2,
campo1 - campo2 as campo_virtual,
campo3,
case when campo_virtual = 1 then 5 else 0 end as segundo_campo_virtual
from tabla;
Esto lo puedo hacer en access sin ningun problema, pero en
postgresql no reconoce el campo_virtual.
¿Es que postgresql no soporta esta consulta o existe algun otro
metodo para lograr esta tecnica?
Nota: (campo1 - campo2) en realidad es una compleja consulta que se
usa varias veces lineas abajo.
I believe you're asking whether it's not supported to reference column
aliases further on in the query? You got that right, they don't get
computed until the final stage of the query.
A workaround is as follows:
select campo1,
campo2,
campo_virtual,
campo3,
case when campo_virtual = 1 then 5 else 0 end as segundo_campo_virtual
from (select *, campo1 - campo2 as campo_virtual from tabla) as tabla;
Alban Hertroys
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