Comments on: How to simulate FULL OUTER JOIN in MySQL http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/ Stay curious! Fri, 29 Aug 2008 05:05:27 +0000 http://wordpress.org/?v=2.2.2 By: Xaprb http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14289 Xaprb Wed, 12 Mar 2008 23:53:06 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14289 It turns out that FULL OUTER JOIN isn't possible no matter what. The reasons are kind of technical. You should be able to get the columns in the order you want if you specify them explicitly. It turns out that FULL OUTER JOIN isn’t possible no matter what. The reasons are kind of technical.

You should be able to get the columns in the order you want if you specify them explicitly.

]]> By: Mark http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14288 Mark Wed, 12 Mar 2008 23:41:09 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14288 Thanks for a useful post. Am I right that a full outer join implementation is not possible using MySQL's NATURAL joins? I'm struggling to get a result where the column joined on does not appear twice. NATURAL joins achieve this but return the columns in different orders... any ideas? Thanks for a useful post. Am I right that a full outer join implementation is not possible using MySQL’s NATURAL joins? I’m struggling to get a result where the column joined on does not appear twice. NATURAL joins achieve this but return the columns in different orders… any ideas?

]]> By: Garry http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14243 Garry Fri, 22 Feb 2008 14:29:14 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14243 Its Wonderful! Explanation is best ......... even newbies like me can understand this better. Thanks a lot! Its Wonderful! Explanation is best ……… even newbies like me can understand this better.
Thanks a lot!

]]> By: Dan http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14148 Dan Sat, 12 Jan 2008 00:01:35 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-14148 Awesome article, helped me big time. -Dan Awesome article, helped me big time.

-Dan

]]> By: Chris Chou’s Homeworld » 在主键相关的查询中，模拟MySQL的全外联接 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-13563 Chris Chou’s Homeworld » 在主键相关的查询中，模拟MySQL的全外联接 Tue, 23 Oct 2007 12:07:28 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-13563 [...] http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/ [...] […] http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/ […]

]]> By: Xaprb http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6467 Xaprb Thu, 10 May 2007 12:03:18 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6467 <p>The MySQL manual explains what you need to do in the section on <a href="http://dev.mysql.com/doc/refman/5.0/en/union.html" rel="nofollow">UNION syntax</a>.</p> The MySQL manual explains what you need to do in the section on UNION syntax.

]]> By: kelmer http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6465 kelmer Thu, 10 May 2007 06:58:43 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6465 <p>I tried this:</p> <pre>(select * from apples as a left outer join oranges as o on a.price= o.price) union all (select * from applesas a right outer join oranges as o on a.price= o.price where a.price is null) order by a.price</pre> <p>and I get an error saying: "#1250 - Table 'a' from one of the SELECTs cannot be used in global ORDER clause " If I use this instead</p> <pre>select * from apples as a left outer join oranges as o on a.price = o.price union all select * from apples as a right outer join oranges as o on a.price = o.price where a.price is null order by a.price</pre> <p>I get this: "#1109 - Unknown table 'a' in order clause " Where and how should I puit the ORDER BY sentence?</p> I tried this:

(select * from apples as a
   left outer join oranges as o on a.price= o.price)
union all
(select * from applesas a
   right outer join oranges as o on a.price= o.price
where a.price is null)
order by a.price

and I get an error saying: “#1250 - Table ‘a’ from one of the SELECTs cannot be used in global ORDER clause “

If I use this instead

select * from apples as a
   left outer join oranges as o on a.price = o.price
union all
select * from apples as a
   right outer join oranges as o on a.price = o.price
where a.price is null
order by a.price

I get this:

“#1109 - Unknown table ‘a’ in order clause “

Where and how should I puit the ORDER BY sentence?

]]> By: Xaprb http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6455 Xaprb Thu, 10 May 2007 02:25:54 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6455 <p>You can just add ORDER BY as normal at the end of the query.</p> You can just add ORDER BY as normal at the end of the query.

]]> By: kelmer http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6451 kelmer Wed, 09 May 2007 20:23:00 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-6451 <p>Hi, Using your method, how can I use an ORDER BY sentence to order the rows by the common attribute (in your case, price)?</p> Hi,

Using your method, how can I use an ORDER BY sentence to order the rows by the common attribute (in your case, price)?

]]> By: Matthew Montgomery http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-3374 Matthew Montgomery Thu, 25 Jan 2007 17:05:50 +0000 http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/#comment-3374 <p>For anyone curious, method #1 CAN be extended to handle more than 2 tables... It just gets ugly. Basically, for each table LEFT JOIN all other tables to it, Then union each of those together.</p> <pre>CREATE TABLE `table1` ( `f1` int(11) default NULL, `gid` int(11) default NULL ) ENGINE=MyISAM; CREATE TABLE `table2`... CREATE TABLE `table3`... INSERT INTO table1 VALUES(1,1), (4,1), (7,1), (10,3), (13,4), (16,4), (19,4), (22,6); INSERT INTO table2 VALUES(2,1), (5,2), (8,2), (11,3), (14,4), (17,5), (20,5), (23,6); INSERT INTO table3 VALUES(3,2), (6,2), (9,3), (12,3), (15,5), (18,5), (21,6), (24,6);</pre> <p>Here I'm trying to get the SUM of each group of numbers within a single table and display them together in the same result so I need a subquery here... i.e. table1, group 1 is 1+4+7 = 12; table3, group 2 is 3+6 = 9 ....</p> <pre>(SELECT t1.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3 FROM (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1 LEFT JOIN (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2 ON (t1.gid = t2.gid) LEFT JOIN (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3 ON (t1.gid = t3.gid) ) UNION ( SELECT t2.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3 FROM (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2 LEFT JOIN (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1 ON (t2.gid = t1.gid) LEFT JOIN (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3 ON (t2.gid = t3.gid) ) UNION ( SELECT t3.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3 FROM (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3 LEFT JOIN (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1 ON (t3.gid = t1.gid) LEFT JOIN (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2 ON (t3.gid = t2.gid) ) ORDER BY gid; +------+------+------+------+ | gid | sum1 | sum2 | sum3 | +------+------+------+------+ | 1 | 12 | 2 | 0 | | 2 | 0 | 13 | 9 | | 3 | 10 | 11 | 21 | | 4 | 48 | 14 | 0 | | 5 | 0 | 37 | 33 | | 6 | 22 | 23 | 45 | +------+------+------+------+</pre> For anyone curious, method #1 CAN be extended to handle more than 2 tables… It just gets ugly. Basically, for each table LEFT JOIN all other tables to it, Then union each of those together.

CREATE TABLE `table1` (
  `f1` int(11) default NULL,
  `gid` int(11) default NULL
) ENGINE=MyISAM;

CREATE TABLE `table2`...

CREATE TABLE `table3`...

INSERT INTO table1 VALUES(1,1), (4,1), (7,1), (10,3), (13,4), (16,4), (19,4), (22,6);
INSERT INTO table2 VALUES(2,1), (5,2), (8,2), (11,3), (14,4), (17,5), (20,5), (23,6);
INSERT INTO table3 VALUES(3,2), (6,2), (9,3), (12,3), (15,5), (18,5), (21,6), (24,6);

Here I’m trying to get the SUM of each group of numbers within a single table and display them together in the same result so I need a subquery here… i.e. table1, group 1 is 1+4+7 = 12; table3, group 2 is 3+6 = 9 ….

(SELECT t1.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3
  FROM (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1
  LEFT JOIN (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2 ON (t1.gid = t2.gid)
  LEFT JOIN (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3 ON (t1.gid = t3.gid)
) UNION (
SELECT t2.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3
  FROM (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2
  LEFT JOIN (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1 ON (t2.gid = t1.gid)
  LEFT JOIN (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3 ON (t2.gid = t3.gid)
) UNION (
SELECT t3.gid, IFNULL(t1.sum1, 0) AS sum1, IFNULL(t2.sum2, 0) AS sum2, IFNULL(t3.sum3, 0) AS sum3
  FROM (SELECT sum(f1) AS sum3, gid FROM table3 GROUP BY gid) AS t3
  LEFT JOIN (SELECT sum(f1) AS sum1, gid FROM table1 GROUP BY gid) AS t1 ON (t3.gid = t1.gid)
  LEFT JOIN (SELECT sum(f1) AS sum2, gid FROM table2 GROUP BY gid) AS t2 ON (t3.gid = t2.gid)
) ORDER BY gid;
+------+------+------+------+
| gid  | sum1 | sum2 | sum3 |
+------+------+------+------+
|    1 |   12 |    2 |    0 |
|    2 |    0 |   13 |    9 |
|    3 |   10 |   11 |   21 |
|    4 |   48 |   14 |    0 |
|    5 |    0 |   37 |   33 |
|    6 |   22 |   23 |   45 |
+------+------+------+------+
]]>