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 Transact-SQL (2008)
 table `forums` where register threads

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mrivero1961
Starting Member

7 Posts

Posted - 2013-02-19 : 11:54:05
Hello everyone.

Thanks all in advance for any help and suggestions.
I've the table `forums` where register threads, I need in output:
  • all threads without replies;
  • for threads with replies, the last reply.

I tried this query but is a problem: in output not are visible the new threads without replies.

This version where use LEFT OUTER JOIN return this new output, the row # 2 -b.id = 394- is too ...

Please check this:
A.ID,
A.connected,
B.id,
B.connected,
A.datum,
B.datum_update,
A.title,
A.author,
B.message,
B.last_replies
FROM
forums a
LEFT OUTER JOIN forums b ON a.id = b.connected
LEFT OUTER JOIN (
SELECT
connected,
max(datum_update) AS max_date
FROM
forums
GROUP BY
connected
) dt ON (b.connected, b.datum_update) = (dt.connected, dt.max_date)
WHERE
A.connected = 0
ORDER BY
dt.max_date DESC;
+-----+-----------+------+-----------+---------------------+---------------------+-----------------+-------------+----------+--------------+
| ID | connected | id | connected | datum | datum_update | title | author | message | last_replies |
+-----+-----------+------+-----------+---------------------+---------------------+-----------------+-------------+----------+--------------+
| 392 | 0 | 395 | 392 | 2012-08-16 11:19:16 | 2013-01-24 01:17:00 | help me | Sandra | regards | Sammy |
| 392 | 0 | 394 | 392 | 2012-08-16 11:19:16 | 2012-08-24 00:08:00 | help me | Sandra | hi there | admin |
| 396 | 0 | NULL | NULL | 2013-02-16 21:28:42 | NULL | new thread | Rudy | NULL | NULL |
| 397 | 0 | NULL | NULL | 2013-02-18 21:35:59 | NULL | post new thread | swampBoogie | NULL | NULL |
+-----+-----------+------+-----------+---------------------+---------------------+-----------------+-------------+----------+--------------+
4 rows in set

James K
Master Smack Fu Yak Hacker

3873 Posts

Posted - 2013-02-19 : 12:18:21
If I understood your requirements correctly, something like shown below should work
SELECT * FROM 
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY datum_update DESC) AS RN
FROM
Forums
) WHERE RN = 1;
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mrivero1961
Starting Member

7 Posts

Posted - 2013-02-19 : 12:54:20
thank you for help, but in the query I've error:


SELECT * FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY datum_update DESC) AS RN
FROM
Forums
) WHERE RN = 1;

ERROR [42000] - [SQL Server] Incorrect syntax near the keyword 'WHERE'.

-- ----------------------------
-- Table structure for [dbo].[forums]
-- ----------------------------
DROP TABLE [dbo].[forums]
GO
CREATE TABLE [dbo].[forums] (
[id] int NULL ,
[connected] int NULL ,
[datum] datetime NULL ,
[datum_updated] datetime NULL ,
[title] nvarchar(255) NULL ,
[author] nvarchar(255) NULL ,
[message] nvarchar(255) NULL ,
[last_replies] nvarchar(255) NULL
)


GO

-- ----------------------------
-- Records of forums
-- ----------------------------
INSERT INTO [dbo].[forums] ([id], [connected], [datum], [datum_updated], [title], [author], [message], [last_replies]) VALUES (N'392', N'0', N'2012-08-16 11:19:16.000', N'2012-08-16 11:08:00.000', N'help me', N'Sandra', N'hello my friend', N'Sandra');
GO
INSERT INTO [dbo].[forums] ([id], [connected], [datum], [datum_updated], [title], [author], [message], [last_replies]) VALUES (N'394', N'392', N'2012-08-24 12:15:27.000', N'2012-08-24 00:08:00.000', N'help me', N'admin', N'hi there', N'admin');
GO
INSERT INTO [dbo].[forums] ([id], [connected], [datum], [datum_updated], [title], [author], [message], [last_replies]) VALUES (N'395', N'392', N'2013-01-24 13:17:27.000', N'2013-01-24 01:17:00.000', N'help me', N'Sammy', N'regards', N'Sammy');
GO
INSERT INTO [dbo].[forums] ([id], [connected], [datum], [datum_updated], [title], [author], [message], [last_replies]) VALUES (N'396', N'0', N'2013-02-16 21:28:42.000', N'2013-02-16 21:28:49.000', N'new thread', N'Rudy', N'this is new thread', N'Rudy');
GO
INSERT INTO [dbo].[forums] ([id], [connected], [datum], [datum_updated], [title], [author], [message], [last_replies]) VALUES (N'397', N'0', N'2013-02-18 21:35:59.000', N'2013-02-18 21:36:04.000', N'post new thread', N'swampBoogie', N'this is my new thread', N'swampBoogie');
GO
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James K
Master Smack Fu Yak Hacker

3873 Posts

Posted - 2013-02-19 : 12:59:39
I had missed an alias - that is why you got a parsing error. See below
...
FROM
Forums
) AS s WHERE RN = 1;
But, that is not going to give you the results you are looking for if there should be only three rows in the desired output.

Can there be more than one level in the thread? For example, can there be another row which has connected = 394?
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mrivero1961
Starting Member

7 Posts

Posted - 2013-02-19 : 13:17:23
quote:
Can there be more than one level in the thread? For example, can there be another row which has connected = 394?


No, not possible.

This is the output correct:
id	connected	datum			datum_updated		title		author		message			last_replies	RN
395 392 24/01/2013 13.17 24/01/2013 1.17 help me Sammy regards Sammy 1
396 0 16/02/2013 21.28 16/02/2013 21.28 new thread Rudy this is new thread Rudy 1
397 0 18/02/2013 21.35 18/02/2013 21.36 post new thread swampBoogie this is my new thread swampBoogie 1

with your suggestion I've:
id	connected	datum			datum_updated		title		author		message			last_replies	RN
392 0 16/08/2012 11.19 16/08/2012 11.08 help me Sandra hello my friend Sandra 1
394 392 24/08/2012 12.15 24/08/2012 0.08 help me admin hi there admin 1
395 392 24/01/2013 13.17 24/01/2013 1.17 help me Sammy regards Sammy 1
396 0 16/02/2013 21.28 16/02/2013 21.28 new thread Rudy this is new thread Rudy 1
397 0 18/02/2013 21.35 18/02/2013 21.36 post new thread swampBoogie this is my new thread swampBoogie 1
SELECT * FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY datum_updated DESC) AS RN
FROM
Forums
) AS s WHERE RN = 1;

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visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2013-02-19 : 13:20:43
should be


SELECT * FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY IDtitle ORDER BY datum_updated DESC) AS RN
FROM
Forums
) AS s WHERE RN = 1;

i guess

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

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mrivero1961
Starting Member

7 Posts

Posted - 2013-02-19 : 13:25:51
quote:
Originally posted by visakh16

should be


SELECT * FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY IDtitle ORDER BY datum_updated DESC) AS RN
FROM
Forums
) AS s WHERE RN = 1;

i guess

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/





thank you, this version working!
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visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2013-02-20 : 01:21:22
welcome

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

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