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* joining from multiple tables
@ 2003-01-16 01:43 Joseph Shraibman <jks@selectacast.net>
2003-01-16 02:02 ` Re: joining from multiple tables Stephan Szabo <sszabo@megazone23.bigpanda.com>
0 siblings, 1 reply; 2+ messages in thread
From: Joseph Shraibman @ 2003-01-16 01:43 UTC (permalink / raw)
To: pgsql-sql
I have a table I want to join on, but the conditions that restrict it span more than one
table. For example:
create table num_tab (thekey int primary key, val int, class char);
create table class_tab (class char primary key, tkey int);
create table txt_tab (thekey int primary key, class int, txt text);
insert into num_tab values (1, 1, 'o');
insert into num_tab values (2, 2, 'e');
insert into num_tab values (3, 3, 'o');
insert into num_tab values (4, 4, 'e');
insert into num_tab values (5, 5, 'o');
insert into num_tab values (6, 6, 'e');
insert into class_tab values('o', 1);
insert into class_tab values('e', 2);
insert into txt_tab values (2, 2,'two');
insert into txt_tab values (4, 2,'four');
insert into txt_tab values (6, 2,'six');
select distinct n.thekey, n.val, t.txt FROM num_tab n LEFT JOIN txt_tab t ON n.thekey =
t.thekey
WHERE n.thekey < 5 AND t.class = class_tab.tkey AND n.class = class_tab.class;
produces:
thekey | val | txt
--------+-----+------
2 | 2 | two
4 | 4 | four
... which is not what we want, because 1,3, and 5 aren't included, but:
select distinct n.thekey, n.val, t.txt FROM num_tab n LEFT JOIN txt_tab t ON n.thekey =
t.thekey AND t.class = class_tab.tkey AND n.class = class_tab.class
WHERE n.thekey < 5;
produces:
NOTICE: Adding missing FROM-clause entry for table "class_tab"
ERROR: JOIN/ON clause refers to "class_tab", which is not part of JOIN
So how do I do this?
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: joining from multiple tables
2003-01-16 01:43 joining from multiple tables Joseph Shraibman <jks@selectacast.net>
@ 2003-01-16 02:02 ` Stephan Szabo <sszabo@megazone23.bigpanda.com>
0 siblings, 0 replies; 2+ messages in thread
From: Stephan Szabo @ 2003-01-16 02:02 UTC (permalink / raw)
To: Joseph Shraibman <jks@selectacast.net>; +Cc: pgsql-sql
On Wed, 15 Jan 2003, Joseph Shraibman wrote:
> select distinct n.thekey, n.val, t.txt FROM num_tab n LEFT JOIN txt_tab t ON n.thekey =
> t.thekey
> WHERE n.thekey < 5 AND t.class = class_tab.tkey AND n.class = class_tab.class;
> produces:
Note that the above uses the non-standard postgres behavior of adding from
clauses, it's not technically valid SQL.
> thekey | val | txt
> --------+-----+------
> 2 | 2 | two
> 4 | 4 | four
> ... which is not what we want, because 1,3, and 5 aren't included, but:
>
> select distinct n.thekey, n.val, t.txt FROM num_tab n LEFT JOIN txt_tab t ON n.thekey =
> t.thekey AND t.class = class_tab.tkey AND n.class = class_tab.class
> WHERE n.thekey < 5;
> produces:
> NOTICE: Adding missing FROM-clause entry for table "class_tab"
> ERROR: JOIN/ON clause refers to "class_tab", which is not part of JOIN
>
> So how do I do this?
I think you want something like:
select distinct n.thekey, n.val, t.txt FROM class_tab JOIN num_tab n
using (class) LEFT JOIN txt_tab t on (t.thekey=n.thekey and t.class =
class_tab.tkey);
^ permalink raw reply [nested|flat] 2+ messages in thread
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2003-01-16 01:43 joining from multiple tables Joseph Shraibman <jks@selectacast.net>
2003-01-16 02:02 ` Stephan Szabo <sszabo@megazone23.bigpanda.com>
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