[Tutor] Table Joins

Terry Carroll carroll at tjc.com
Wed Aug 22 18:22:36 CEST 2007


On Wed, 22 Aug 2007, Terry Carroll wrote:

> If you want to pull them out of the database as a single table....
> I was wondering that myself the other day.  I was planning on looking 
> into whether you could just do a FULL OUTER JOIN (which is essentially a 
> union operation) on both tables.  I haven't checked that out, yet; you 
> might want to look into it.

Actually, I'm making this much too hard (especially as I think SQLite, the 
only SQL database I have access to, apparently does not directly support 
FULL OUTER JOIN).  But I just discovered the UNION keyword on the SELECT 
statement:

sqlite> create table a1 (v1 int primary key, v2 text);
sqlite> create table a2 (v1 int primary key, v2 text);
sqlite> insert into a1 values(1, 'a');
sqlite> insert into a1 values(2, 'b');
sqlite> insert into a1 values(3, 'c');
sqlite> insert into a1 values(4, 'd');
sqlite> insert into a1 values(5, 'e');
sqlite> insert into a2 values(1, 'a');
sqlite> insert into a2 values(5, 'e');
sqlite> insert into a2 values(9, 'i');
sqlite> insert into a2 values(15, 'o');
sqlite> insert into a2 values(21, 'u');
sqlite> select * from a1;
1|a
2|b
3|c
4|d
5|e
sqlite> select * from a2;
1|a
5|e
9|i
15|o
21|u
sqlite> select * from a1 union select * from a2;
1|a
2|b
3|c
4|d
5|e
9|i
15|o
21|u


Would that do what the OP wanted?  You'd have to make the union select a 
Python call, of course.



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