Fwd: [PHP-DB] Select from multiple tables
-- Vidarebefordrat meddelande -- Från: Carl Michael Skog cms...@gmail.com Datum: 1 mars 2012 17:12 Ämne: Re: [PHP-DB] Select from multiple tables Till: Kranthi Krishna kranthi...@gmail.com It seems to me that you are mixing two semantically different things(board_entries and schooltypeentries, both related to school). These have no relation to each other(at least no one shown here, so you get a cartesian join over these tables(within the restrictions in the where clause)). Still, you want to lump them together in the same result set. The question is why ? Den 1 mars 2012 06:46 skrev Kranthi Krishna kranthi...@gmail.com: Hi all, SELECT DISTINCT s.Title, b.Board_id, t.type FROM school s, board_entries b, schooltypeentries t WHERE s.School_id = 1698 AND b.School_id = 1698 AND t.schoolid = 1698 this SQL query gives me Kendriya Vidyalaya 15 Kick Boxing Kendriya Vidyalaya 15 Karate Kendriya Vidyalaya 32 Kick Boxing Kendriya Vidyalaya 32 Karate as I stated earlier. Now using php.net/array_search php.net/foreach and php.net/mysql_fetch_assoc I can easily convert that into array name = 'Kendriya Vidyalaya' board_id = array 1 = 15 2 = 32 type = array 1 = 'Kick Boxing' 2 = 'Karate' I am wondering if there is a better way. For example if I am able to get something like Kendriya Vidyalaya 15 Kick Boxing NULLNULLKarate NULL32 NULL NULLNULLNULL I can use php.net/is_null instead of php.net/array_search I dont think this problem is specific to me. Please suggest some best practices in this case. Kranthi. http://goo.gl/e6t3 On 1 March 2012 10:25, Karl DeSaulniers k...@designdrumm.com wrote: Try DISTINCT On Feb 29, 2012, at 10:28 PM, Amit Tandon wrote: Dear Kranthi You have to be clear what you decide especially when you are getting multiple rows. To get just a single row you can use LIMIT clause. But it would return only one row. Now you have to decide which row. So i think you decide on what you require and see how can you uniquely identify that row regds amit The difference between fiction and reality? Fiction has to make sense. On Thu, Mar 1, 2012 at 9:45 AM, Kranthi Krishna kranthi...@gmail.comwrote: Hi, The examples I saw were regarding cartesian join not inner join. I will read about inner joins. Also, the example i mentioned seems to be a mistake. Both school and type will not be similar at the same time Kranthi. http://goo.gl/e6t3 On 1 March 2012 09:26, Kranthi Krishna kranthi...@gmail.com wrote: Hi, Thanks for the input. I have seen some tutorials on joins, they all suggest that MySql returns multiple rows For example -- School | Board 1 -- School | Board 1 - Now if I have another one-to-many relation --- School | Board 1 | Type 1 --- School | Board 1 | Type 2 --- School | Board 2 | Type 1 --- School | Board 2 | Type 2 Using UNIQUE or something similar (like php.net/array_search ) causes problems when Type 1 = Type 2 etc. Kranthi. http://goo.gl/e6t3 On 29 February 2012 19:43, Michael Stowe mikegst...@gmail.com wrote: Select table1.item1, table2.item1 from table1 inner join table2 on table1.key = table2.foreignKey Where... You can also utilize left and right join to get data if there isn't a direct match (ie customer may not have ordered anything so you want to do a left join on orders as there may not be any order data but you still want to get the customer info). Hope that helps, Mike Sent from my iPhone On Feb 29, 2012, at 8:01 AM, Kranthi Krishna kranthi...@gmail.com wrote: Hi all, Say I have an object like array schoolName = string board = array string string I generally create two MySql tables schools: id PRIMARY KEY, SchoolName boards: id FOREGIN KEY refers Table A(id), board and then do two selects. The problem is that, the number of selects increase as the number of one-to-many relationships increase. Is there a better way to do this ? I have to extend an existing code so I cannot use any libraries like doctrine Kranthi. http://goo.gl/e6t3 -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php Karl DeSaulniers Design Drumm http://designdrumm.com -- PHP Database Mailing List
Re: [PHP-DB] Select from multiple tables
I am a little confused It seems to me that you are mixing two semantically different things I agree. But since both of them are attributes of school so I have to. so you get a cartesian join over these tables(within the restrictions in the where clause) If I am not mistaken INNER JOIN is Cartesian join with where clause Still, you want to lump them together in the same result set. You misunderstood me. I never said that I want a single row set. The following query SELECT s.Title, b.Board_id, t.type FROM (SELECT Title FROM school where School_id = 1698) s, (SELECT GROUP_CONCAT(Board_id) AS Board_id FROM board_entries WHERE School_id = 1698) b, (SELECT GROUP_CONCAT(type) AS type FROM schooltypeentries WHERE schoolid = 1698) t returns me a single row set. But I am aware that this is not practical All I want to do is to restore an object with multiple one-to-many relations Kranthi. http://goo.gl/e6t3 On 1 March 2012 21:47, Carl Michael Skog cms...@gmail.com wrote: -- Vidarebefordrat meddelande -- Från: Carl Michael Skog cms...@gmail.com Datum: 1 mars 2012 17:12 Ämne: Re: [PHP-DB] Select from multiple tables Till: Kranthi Krishna kranthi...@gmail.com It seems to me that you are mixing two semantically different things(board_entries and schooltypeentries, both related to school). These have no relation to each other(at least no one shown here, so you get a cartesian join over these tables(within the restrictions in the where clause)). Still, you want to lump them together in the same result set. The question is why ? Den 1 mars 2012 06:46 skrev Kranthi Krishna kranthi...@gmail.com: Hi all, SELECT DISTINCT s.Title, b.Board_id, t.type FROM school s, board_entries b, schooltypeentries t WHERE s.School_id = 1698 AND b.School_id = 1698 AND t.schoolid = 1698 this SQL query gives me Kendriya Vidyalaya 15 Kick Boxing Kendriya Vidyalaya 15 Karate Kendriya Vidyalaya 32 Kick Boxing Kendriya Vidyalaya 32 Karate as I stated earlier. Now using php.net/array_search php.net/foreach and php.net/mysql_fetch_assoc I can easily convert that into array name = 'Kendriya Vidyalaya' board_id = array 1 = 15 2 = 32 type = array 1 = 'Kick Boxing' 2 = 'Karate' I am wondering if there is a better way. For example if I am able to get something like Kendriya Vidyalaya 15 Kick Boxing NULL NULL Karate NULL 32 NULL NULL NULL NULL I can use php.net/is_null instead of php.net/array_search I dont think this problem is specific to me. Please suggest some best practices in this case. Kranthi. http://goo.gl/e6t3 On 1 March 2012 10:25, Karl DeSaulniers k...@designdrumm.com wrote: Try DISTINCT On Feb 29, 2012, at 10:28 PM, Amit Tandon wrote: Dear Kranthi You have to be clear what you decide especially when you are getting multiple rows. To get just a single row you can use LIMIT clause. But it would return only one row. Now you have to decide which row. So i think you decide on what you require and see how can you uniquely identify that row regds amit The difference between fiction and reality? Fiction has to make sense. On Thu, Mar 1, 2012 at 9:45 AM, Kranthi Krishna kranthi...@gmail.comwrote: Hi, The examples I saw were regarding cartesian join not inner join. I will read about inner joins. Also, the example i mentioned seems to be a mistake. Both school and type will not be similar at the same time Kranthi. http://goo.gl/e6t3 On 1 March 2012 09:26, Kranthi Krishna kranthi...@gmail.com wrote: Hi, Thanks for the input. I have seen some tutorials on joins, they all suggest that MySql returns multiple rows For example -- School | Board 1 -- School | Board 1 - Now if I have another one-to-many relation --- School | Board 1 | Type 1 --- School | Board 1 | Type 2 --- School | Board 2 | Type 1 --- School | Board 2 | Type 2 Using UNIQUE or something similar (like php.net/array_search ) causes problems when Type 1 = Type 2 etc. Kranthi. http://goo.gl/e6t3 On 29 February 2012 19:43, Michael Stowe mikegst...@gmail.com wrote: Select table1.item1, table2.item1 from table1 inner join table2 on table1.key = table2.foreignKey Where... You can also utilize left and right join to get data if there isn't a direct match (ie customer may not have ordered anything so you want to do a left join on orders as there may not be any order data but you still want to get the customer info).
