Thread: SQL command join question

Hi,

I have three tables t1(a, b, c, d), t2(a, b, c, k), and t3(c, e). I need to 
outer join them as shown below, but only have all tuples from t1 as output. 
But the following syntax does not allow me to do so.

SELECT t1.*
FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on 
(t1.c=t3.c);

I'm getting the following error message:
ERROR:  invalid reference to FROM-clause entry for table "t1"
HINT:  There is an entry for table "t1", but it cannot be referenced from 
this part of the query.

I'll be grateful if someone may help me with this.

Thanks,
Ehab

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Would this be more appropriate...?SELECT t1.*FROM t1OUTER JOIN t2 ON (t1.a=t2.a AND t1.b=t2.b)OUTER JOIN t3 ON
(t1.c=t3.c);


-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org]
On Behalf Of Ehab Galal
Sent: Thursday, 30 November 2006 11:42
To: pgsql-sql@postgresql.org
Subject: [SQL] SQL command join question

Hi,

I have three tables t1(a, b, c, d), t2(a, b, c, k), and t3(c, e). I need to
outer join them as shown below, but only have all tuples from t1 as output.
But the following syntax does not allow me to do so.

SELECT t1.*
FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on
(t1.c=t3.c);

I'm getting the following error message:
ERROR:  invalid reference to FROM-clause entry for table "t1"
HINT:  There is an entry for table "t1", but it cannot be referenced from
this part of the query.

I'll be grateful if someone may help me with this.

Thanks,
Ehab

_________________________________________________________________
Fixing up the home? Live Search can help
http://imagine-windowslive.com/search/kits/default.aspx?kit=improve&locale=e
n-US&source=hmemailtaglinenov06&FORM=WLMTAG


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On Wed, 29 Nov 2006, Ehab Galal wrote:

> I have three tables t1(a, b, c, d), t2(a, b, c, k), and t3(c, e). I need to
> outer join them as shown below, but only have all tuples from t1 as output.
> But the following syntax does not allow me to do so.
>
> SELECT t1.*
> FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on
> (t1.c=t3.c);

I think you don't want to alias the output of the t1/t2 join to t if
you're planning to continue referring to t1 in the rest of the query since
I think the alias is going to hide the original t1 name.

I'm not sure which outer join you were trying to use, but assuming left
for now, I think something likeSELECT t1.* FROM t1 left outer join t2 on (t1.a=t2.a and t1.b=t2.b) left outer join t3
on(t1.c=t3.c);
 
might work for you.

> SELECT t1.*
> FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on
       ^^
 
> (t1.c=t3.c);  ^^  -- which one t or t1?

> I'm getting the following error message:
> ERROR:  invalid reference to FROM-clause entry for table "t1"
> HINT:  There is an entry for table "t1", but it cannot be referenced from 
> this part of the query.

I am not use if I am about to give to the correct advice, but here is what stands out at me:

when you specify an outer join, I believe that you have to specify whether it is a
(left|right|full).

Also you are using a "t" to alias the (t1 .. t2 on (...)).  First of all, I am not sure this is
good syntax, but if I am wrong I will have learned something new.  That aside, if it is legal
syntax, I don't believe that you can refer to any of it's enternal tables any more.  So (t1.c=...)
should really be (t.c=...).

this is what I expect would work:

select          *
from       t1
left outer join       t2
on    ((t1.a,t1.b) = (t2.a,t2.b))
left outer join       t3
on    (t1.c = t3.c)
;

Regards,

Richard Broersma Jr.

"Ehab Galal" <ehabgalal123@hotmail.com> writes:
> SELECT t1.*
> FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on 
> (t1.c=t3.c);

> ERROR:  invalid reference to FROM-clause entry for table "t1"
> HINT:  There is an entry for table "t1", but it cannot be referenced from 
> this part of the query.

Drop the alias on the outer join (the "t").  Per SQL spec, that masks
table names (and aliases) within the join from the rest of the query.
        regards, tom lane