Comments on: Basic SQL join semantics http://blog.mclaughlinsoftware.com Michael McLaughlin's Technical Blog Wed, 28 Jul 2010 12:12:28 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Kyle Hailey http://blog.mclaughlinsoftware.com/oracle-sql-programming/basic-sql-join-semantics/comment-page-1/#comment-6184 Kyle Hailey Fri, 26 Jun 2009 16:59:45 +0000 http://blog.mclaughlinsoftware.com/?page_id=1290#comment-6184 Nice writeup. I like the graphic on left, right and inner join. I did an extension of it here: http://db-optimizer.blogspot.com/2009/06/sql-joins.html Nice writeup. I like the graphic on left, right and inner join. I did an extension of it here:

http://db-optimizer.blogspot.com/2009/06/sql-joins.html

]]> By: maclochlainn http://blog.mclaughlinsoftware.com/oracle-sql-programming/basic-sql-join-semantics/comment-page-1/#comment-913 maclochlainn Sun, 15 Feb 2009 21:06:30 +0000 http://blog.mclaughlinsoftware.com/?page_id=1290#comment-913 Thanks for the observation. I concur wholeheartedly with your observations that there's nothing natural about natural joins. :-) BTW, that's a nice page. Thanks for the observation. I concur wholeheartedly with your observations that there’s nothing natural about natural joins. :-) BTW, that’s a nice page.

]]> By: Gints Plivna http://blog.mclaughlinsoftware.com/oracle-sql-programming/basic-sql-join-semantics/comment-page-1/#comment-911 Gints Plivna Sun, 15 Feb 2009 20:12:42 +0000 http://blog.mclaughlinsoftware.com/?page_id=1290#comment-911 Natural join can be also outer join. Actually I'd say it is just another (potentially dangerous!!!) syntactical notation. And I've tried to explain joins here http://www.gplivna.eu/papers/sql_join_types.htm Natural join can be also outer join. Actually I’d say it is just another (potentially dangerous!!!) syntactical notation. And I’ve tried to explain joins here http://www.gplivna.eu/papers/sql_join_types.htm

]]> By: Laurent Schneider http://blog.mclaughlinsoftware.com/oracle-sql-programming/basic-sql-join-semantics/comment-page-1/#comment-722 Laurent Schneider Wed, 04 Feb 2009 10:53:43 +0000 http://blog.mclaughlinsoftware.com/?page_id=1290#comment-722 UNION differs from FULL OUTER JOIN as it will remove duplicates. SELECT ordinal_english_text , ordinal_french_text FROM ordinal_english, ordinal_french WHERE ordinal_english_id(+) = ordinal_french_id UNION SELECT ordinal_english_text , ordinal_french_text FROM ordinal_english, ordinal_french WHERE ordinal_english_id = ordinal_french_id(+); this will remove the duplicates for ordinal_english_text , ordinal_french_text use UNION ALL instead SQL> create table lsc_t1(x number, y number) Table created. SQL> insert into lsc_t1 values(1,1) 1 row created. SQL> insert into lsc_t1 values(1,1) 1 row created. SQL> insert into lsc_t1 values(2,2) 1 row created. SQL> create table lsc_t2(y number, z number) Table created. SQL> insert into lsc_t2 values(2,2) 1 row created. SQL> insert into lsc_t2 values(3,3) 1 row created. SQL> insert into lsc_t2 values(3,3) 1 row created. SQL> commit Commit complete. SQL> select x,y,z from lsc_t1 full join lsc_t2 using (y) order by y X Y Z ---------- ---------- ---------- 1 1 1 1 2 2 2 3 3 3 3 5 rows selected. SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+) order by y X Y Z ---------- ---------- ---------- 1 1 1 1 2 2 2 3 rows selected. SQL> select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y order by y X Y Z ---------- ---------- ---------- 2 2 2 3 3 3 3 3 rows selected. SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+) union select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y order by y X Y Z ---------- ---------- ---------- 1 1 2 2 2 3 3 3 rows selected. SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+) union all select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y and lsc_t1.y is null order by y X Y Z ---------- ---------- ---------- 1 1 1 1 2 2 2 3 3 3 3 5 rows selected. UNION differs from FULL OUTER JOIN as it will remove duplicates.

SELECT ordinal_english_text
, ordinal_french_text
FROM ordinal_english, ordinal_french
WHERE ordinal_english_id(+) = ordinal_french_id
UNION
SELECT ordinal_english_text
, ordinal_french_text
FROM ordinal_english, ordinal_french
WHERE ordinal_english_id = ordinal_french_id(+);

this will remove the duplicates for ordinal_english_text , ordinal_french_text

use UNION ALL instead

SQL> create table lsc_t1(x number, y number)
Table created.
SQL> insert into lsc_t1 values(1,1)
1 row created.
SQL> insert into lsc_t1 values(1,1)
1 row created.
SQL> insert into lsc_t1 values(2,2)
1 row created.
SQL> create table lsc_t2(y number, z number)
Table created.
SQL> insert into lsc_t2 values(2,2)
1 row created.
SQL> insert into lsc_t2 values(3,3)
1 row created.
SQL> insert into lsc_t2 values(3,3)
1 row created.
SQL> commit
Commit complete.
SQL> select x,y,z from lsc_t1 full join lsc_t2 using (y) order by y

X Y Z
———- ———- ———-
1 1
1 1
2 2 2
3 3
3 3

5 rows selected.
SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+) order by y

X Y Z
———- ———- ———-
1 1
1 1
2 2 2

3 rows selected.
SQL> select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y order by y

X Y Z
———- ———- ———-
2 2 2
3 3
3 3

3 rows selected.
SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+)
union
select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y order by y

X Y Z
———- ———- ———-
1 1
2 2 2
3 3

3 rows selected.
SQL> select x,lsc_t1.y,z from lsc_t1 , lsc_t2 where lsc_t1.y=lsc_t2.y(+)
union all
select x,lsc_t2.y,z from lsc_t1 , lsc_t2 where lsc_t1.y(+)=lsc_t2.y and lsc_t1.y is null order by y

X Y Z
———- ———- ———-
1 1
1 1
2 2 2
3 3
3 3

5 rows selected.

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