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database row/ record pointers

- by David

Hi I don't know the correct words for what I'm trying to find out about and as such having a hard time googling. I want to know whether its possible with databases (technology independent but would be interested to hear whether its possible with Oracle, MySQL and Postgres) to point to specific rows instead of executing my query again. So I might initially execute a query find some rows of interest and then wish to avoid searching for them again by having a list of pointers or some other metadata which indicates the location on a database which I can go to straight away the next time I want those results. I realise there is caching on databases, but I want to keep these "pointers" else where and as such caching doesn't ultimately solve this problem. Is this just an index and I store the index and look up by this? most of my current tables don't have indexes and I don't want the speed decrease that sometimes comes with indexes. So whats the magic term I've been trying to put into google? Cheers

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MySQL Import Database Error because of Extended Inserts

- by Castgame

Hello all, I'm importing a 400MB(uncompressed) MySQL database. I'm using BIGDUMP, and I am getting this error: Stopped at the line 387. At this place the current query includes more than 300 dump lines. That can happen if your dump file was created by some tool which doesn't place a semicolon followed by a linebreak at the end of each query, or if your dump contains extended inserts. Please read the BigDump FAQs for more infos. I believe the file does contain Extended Inserts, however I have no way to regenerate the database as it has been deleted from the old server. How can I import this database or convert it to be imported? Thanks for any help. Best Nick EDIT: It appears the only viable answer is to separate the extended inserts, but I still need help figuring out how to split the file as the answer below suggests. Please help. Thank you.

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Linux server is only using 60% of memory, then swapping

- by Kamil Kisiel

I've got a Linux server that's running our bacula backup system. The machine is grinding like mad because it's going heavy in to swap. The problem is, it's only using 60% of its physical memory! Here's the output from free -m: free -m total used free shared buffers cached Mem: 3949 2356 1593 0 0 1 -/+ buffers/cache: 2354 1595 Swap: 7629 1804 5824 and some sample output from vmstat 1: procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 0 2 1843536 1634512 0 4188 54 13 2524 666 2 1 1 1 89 9 0 1 11 1845916 1640724 0 388 2700 4816 221880 4879 14409 170721 4 3 63 30 0 0 9 1846096 1643952 0 0 4956 756 174832 804 12357 159306 3 4 63 30 0 0 11 1846104 1643532 0 0 4916 540 174320 580 10609 139960 3 4 64 29 0 0 4 1846084 1640272 0 2336 4080 524 140408 548 9331 118287 3 4 63 30 0 0 8 1846104 1642096 0 1488 2940 432 102516 457 7023 82230 2 4 65 29 0 0 5 1846104 1642268 0 1276 3704 452 126520 452 9494 119612 3 5 65 27 0 3 12 1846104 1641528 0 328 6092 608 187776 636 8269 113059 4 3 64 29 0 2 2 1846084 1640960 0 724 5948 0 111480 0 7751 116370 4 4 63 29 0 0 4 1846100 1641484 0 404 4144 1476 125760 1500 10668 105358 2 3 71 25 0 0 13 1846104 1641932 0 0 5872 828 153808 840 10518 128447 3 4 70 22 0 0 8 1846096 1639172 0 3164 3556 556 74884 580 5082 65362 2 2 73 23 0 1 4 1846080 1638676 0 396 4512 28 50928 44 2672 38277 2 2 80 16 0 0 3 1846080 1628808 0 7132 2636 0 28004 8 1358 14090 0 1 78 20 0 0 2 1844728 1618552 0 11140 7680 0 12740 8 763 2245 0 0 82 18 0 0 2 1837764 1532056 0 101504 2952 0 95644 24 802 3817 0 1 87 12 0 0 11 1842092 1633324 0 4416 1748 10900 143144 11024 6279 134442 3 3 70 24 0 2 6 1846104 1642756 0 0 4768 468 78752 468 4672 60141 2 2 76 20 0 1 12 1846104 1640792 0 236 4752 440 140712 464 7614 99593 3 5 58 34 0 0 3 1846084 1630368 0 6316 5104 0 20336 0 1703 22424 1 1 72 26 0 2 17 1846104 1638332 0 3168 4080 1720 211960 1744 11977 155886 3 4 65 28 0 1 10 1846104 1640800 0 132 4488 556 126016 584 8016 106368 3 4 63 29 0 0 14 1846104 1639740 0 2248 3436 428 114188 452 7030 92418 3 3 59 35 0 1 6 1846096 1639504 0 1932 5500 436 141412 460 8261 112210 4 4 63 29 0 0 10 1846104 1640164 0 3052 4028 448 147684 472 7366 109554 4 4 61 30 0 0 10 1846100 1641040 0 2332 4952 632 147452 664 8767 118384 3 4 63 30 0 4 8 1846084 1641092 0 664 4948 276 152264 292 6448 98813 5 5 62 28 0 Furthermore, the output of top sorted by CPU time seems to support the theory that swap is what's bogging down the system: top - 09:05:32 up 37 days, 23:24, 1 user, load average: 9.75, 8.24, 7.12 Tasks: 173 total, 1 running, 172 sleeping, 0 stopped, 0 zombie Cpu(s): 1.6%us, 1.4%sy, 0.0%ni, 76.1%id, 20.6%wa, 0.1%hi, 0.2%si, 0.0%st Mem: 4044632k total, 2405628k used, 1639004k free, 0k buffers Swap: 7812492k total, 1851852k used, 5960640k free, 436k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ TIME COMMAND 4174 root 17 0 63156 176 56 S 8 0.0 2138:52 35,38 bacula-fd 4185 root 17 0 63352 284 104 S 6 0.0 1709:25 28,29 bacula-sd 240 root 15 0 0 0 0 D 3 0.0 831:55.19 831:55 kswapd0 2852 root 10 -5 0 0 0 S 1 0.0 126:35.59 126:35 xfsbufd 2849 root 10 -5 0 0 0 S 0 0.0 119:50.94 119:50 xfsbufd 1364 root 10 -5 0 0 0 S 0 0.0 117:05.39 117:05 xfsbufd 21 root 10 -5 0 0 0 S 1 0.0 48:03.44 48:03 events/3 6940 postgres 16 0 43596 8 8 S 0 0.0 46:50.35 46:50 postmaster 1342 root 10 -5 0 0 0 S 0 0.0 23:14.34 23:14 xfsdatad/4 5415 root 17 0 1770m 108 48 S 0 0.0 15:03.74 15:03 bacula-dir 23 root 10 -5 0 0 0 S 0 0.0 13:09.71 13:09 events/5 5604 root 17 0 1216m 500 200 S 0 0.0 12:38.20 12:38 java 5552 root 16 0 1194m 580 248 S 0 0.0 11:58.00 11:58 java Here's the same sorted by virtual memory image size: top - 09:08:32 up 37 days, 23:27, 1 user, load average: 8.43, 8.26, 7.32 Tasks: 173 total, 1 running, 172 sleeping, 0 stopped, 0 zombie Cpu(s): 3.6%us, 3.4%sy, 0.0%ni, 62.2%id, 30.2%wa, 0.2%hi, 0.3%si, 0.0%st Mem: 4044632k total, 2404212k used, 1640420k free, 0k buffers Swap: 7812492k total, 1852548k used, 5959944k free, 100k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ TIME COMMAND 5415 root 17 0 1770m 56 44 S 0 0.0 15:03.78 15:03 bacula-dir 5604 root 17 0 1216m 492 200 S 0 0.0 12:38.30 12:38 java 5552 root 16 0 1194m 476 200 S 0 0.0 11:58.20 11:58 java 4598 root 16 0 117m 44 44 S 0 0.0 0:13.37 0:13 eventmond 9614 gdm 16 0 93188 0 0 S 0 0.0 0:00.30 0:00 gdmgreeter 5527 root 17 0 78716 0 0 S 0 0.0 0:00.30 0:00 gdm 4185 root 17 0 63352 284 104 S 20 0.0 1709:52 28,29 bacula-sd 4174 root 17 0 63156 208 88 S 24 0.0 2139:25 35,39 bacula-fd 10849 postgres 18 0 54740 216 108 D 0 0.0 0:31.40 0:31 postmaster 6661 postgres 17 0 49432 0 0 S 0 0.0 0:03.50 0:03 postmaster 5507 root 15 0 47980 0 0 S 0 0.0 0:00.00 0:00 gdm 6940 postgres 16 0 43596 16 16 S 0 0.0 46:51.39 46:51 postmaster 5304 postgres 16 0 40580 132 88 S 0 0.0 6:21.79 6:21 postmaster 5301 postgres 17 0 40448 24 24 S 0 0.0 0:32.17 0:32 postmaster 11280 root 16 0 40288 28 28 S 0 0.0 0:00.11 0:00 sshd 5534 root 17 0 37580 0 0 S 0 0.0 0:56.18 0:56 X 30870 root 30 15 31668 28 28 S 0 0.0 1:13.38 1:13 snmpd 5305 postgres 17 0 30628 16 16 S 0 0.0 0:11.60 0:11 postmaster 27403 postfix 17 0 30248 0 0 S 0 0.0 0:02.76 0:02 qmgr 10815 postfix 15 0 30208 16 16 S 0 0.0 0:00.02 0:00 pickup 5306 postgres 16 0 29760 20 20 S 0 0.0 0:52.89 0:52 postmaster 5302 postgres 17 0 29628 64 32 S 0 0.0 1:00.64 1:00 postmaster I've tried tuning the swappiness kernel parameter to both high and low values, but nothing appears to change the behavior here. I'm at a loss to figure out what's going on. How can I find out what's causing this? Update: The system is a fully 64-bit system, so there should be no question of memory limitations due to 32-bit issues. Update2: As I mentioned in the original question, I've already tried tuning swappiness to all sorts of values, including 0. The result is always the same, with approximately 1.6 GB of memory remaining unused. Update3: Added top output to the above info.

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click and submit button id with jquery

- by user836910

my aim is to submit a button id using jquery into a database im only interested in the button not its value. $("#button").click(function(){ var p = $(this).attr("id"); $.ajax({ type: "POST", url: subpage.php", data: 'b='+p, cache: false, success: function(html) { //process live } }); return false; }); subpage.php $item = $_POST['b']; $query = mysql_query("SELECT * FROM table WHERE id = '25' AND bttnid = '$item'"); if(count($query)==0){ mysql_query("INSERT INTO table VALUES ('','25','$item') "); } it doesn't submit. please assit

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jquery: if ul has li with certain classname?

- by mathiregister

hi guys, i wonder how i can query if a ul has a first-child li with a certain classname? like… <ul> <li>list element 1</li> <li>list element 2</li> </ul> <ul> <li class="whatever">list element 1</li> <li>list element 2</li> </ul> i want to query if ul has a child with classname whatever - do something! is that even possible? thank you

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Rails: find_by_sql and PREPARE stmt FROM... i cant make it work

- by Totty

I have this query and I have an error: images = Image.find_by_sql('PREPARE stmt FROM \' SELECT * FROM images AS i WHERE i.on_id = 1 AND i.on_type = "profile" ORDER BY i.updated_at LIMIT ?, 6\ '; SET @lower_limit := ((5 DIV 6) * 6); EXECUTE stmt USING @lower_limit;') Mysql::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SET @lower_limit := ((5 DIV 6) * 6); EXECUTE stmt USING @lower_limit' at line 1: PREPARE stmt FROM ' SELECT * FROM images AS i WHERE i.on_id = 1 AND i.on_type = "profile" ORDER BY i.updated_at LIMIT ?, 6'; SET @lower_limit := ((5 DIV 6) * 6); EXECUTE stmt USING @lower_limit; EDIT: after finding the answer to: http://stackoverflow.com/questions/2566620/mysql-i-need-to-get-the-offset-of-a-item-in-a-query i need another help here to port it to rails.

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tsql sum data and include default values for missing data

- by markpirvine

Hi, I would like a query that will shouw a sum of columns with a default value for missing data. For example assume I have a table as follows: type_lookup: id name 1 self 2 manager 3 peer And a table as follows data: id type_lookup_id value 1 1 1 2 1 4 3 2 9 4 2 1 5 2 9 6 1 5 7 2 6 8 1 2 9 1 1 After running a query I would like a result set as follows: type_lookup_id value 1 13 2 25 3 0 I would like all rows in type_lookup table to be included in the result set - even if they don't appear in the data table. Any help would be greatly appreciated, Mark

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Stored proc executes >30 secs when called from website, but <1 sec when called from ssms

- by Blootac

I have a stored procedure that is called by a website to display data. Today the web page has started timing out so I got profiler going and saw the query that was taking too long. I then ran the same query in management studio, under the same user login, and it takes less than a second to return. Is there anything obvious that could be causing this? I can't think of a reason why when ASP calls the stored proc it takes 30 secs but when I call it it's fine. Thanks

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Find maximum number of logged on users in SQL

- by lleto

Hi, I want to keep tabs on the number of concurrent users of my application. I therefore log a time_start and a time_stop. If I now want to query the database for the maximum number of logged on users and return the start date, how would I do that. The table looks like this: id | time_start | time_stop ----+---------------------+--------------------- 1 | 2010-03-07 05:40:59 | 2010-03-07 05:41:33 2 | 2010-03-07 06:50:51 | 2010-03-07 10:50:51 3 | 2010-02-21 05:20:00 | 2010-03-07 12:23:44 4 | 2010-02-19 08:21:12 | 2010-03-07 12:37:28 5 | 2010-02-13 05:52:13 | Where time_stop is empty the user is still logged on. In this case I would expect to see 2010-03-07 returned, since all users (5) were logged on at that moment. However if I would run the query with 'where time_start BETWEEN '2010-02-17' AND '2010-02-23' I would expect to see 2010-02-21 with a maximum of 2. Is this possible direct in SQL (using postgres) or do I need to parse the results in PHP? Thanks, lleto

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Ordering by multiple columns in mysql with subquery

- by Scarface

Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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HOw do I limit array to a certain number??

- by mathew

I do have an array which queries database..what I need to do is control this array to a certain number say 10. but I dont want to set LIMIT in mysql query I need to leave that as it is... $result = mysql_query("SELECT * FROM query ORDER BY regtime DESC"); while($row = mysql_fetch_array($result)) { echo "<img src='bullet.gif' align='absmiddle' class='col1ab'><a class='col1ab' href=".$row['web']." >www.".$row['web']."</a><br>"; } How do I limit this array to certain limit??

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HQL: illegal attempt to dereference collection

- by skip

The situation is like this: I have an entity Book that holds a one-to-many relationship with Chapter. Now if I try the query, "from Book book inner join book.chapters chapter where chapter.title like '%hibernate%'", it gives me the desired result. But if I try, "from Book where book.chapters.title like '%hibernate%'", I get the error illegal attempt to dereference collection. The thing is that I only want the collection of Book objects in return and not a collection of pair of Book and Chapter objects in return which I get with the former query. Could someone help me understand?

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How do you get SQLAlchemy to override MySQL "on update CURRENT_TIMESTAMP"

- by nocola

I've inherited an older database that was setup with a "on update CURRENT_TIMESTAMP" put on a field that should only describe an item's creation. With PHP I have been using "timestamp=timestamp" on UPDATE clauses, but in SQLAlchemy I can't seem to force the system to use the set timestamp. Do I have no choice and need to update the MySQL table (millions of rows)? foo = session.query(f).get(int(1)) ts = foo.timestamp setattr(foo, 'timestamp', ts) setattr(foo, 'bar', bar) www_model.www_Session.commit() I have also tried: foo = session.query(f).get(int(1)) setattr(foo, 'timestamp', foo.timestamp) setattr(foo, 'bar', bar) www_model.www_Session.commit()

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Repeat Customers Each Year (Retention)

- by spazzie

I've been working on this and I don't think I'm doing it right. |D Our database doesn't keep track of how many customers we retain so we looked for an alternate method. It's outlined in this article. It suggests you have this table to fill in: Year Number of Customers Number of customers Retained in 2009 Percent (%) Retained in 2009 Number of customers Retained in 2010 Percent (%) Retained in 2010 .... 2008 2009 2010 2011 2012 Total The table would go out to 2012 in the headers. I'm just saving space. It tells you to find the total number of customers you had in your starting year. To do this, I used this query since our starting year is 2008: select YEAR(OrderDate) as 'Year', COUNT(distinct(billemail)) as Customers from dbo.tblOrder where OrderDate >= '2008-01-01' and OrderDate <= '2008-12-31' group by YEAR(OrderDate) At the moment we just differentiate our customers by email address. Then you have to search for the same names of customers who purchased again in later years (ours are 2009, 10, 11, and 12). I came up with this. It should find people who purchased in both 2008 and 2009. SELECT YEAR(OrderDate) as 'Year',COUNT(distinct(billemail)) as Customers FROM dbo.tblOrder o with (nolock) WHERE o.BillEmail IN (SELECT DISTINCT o1.BillEmail FROM dbo.tblOrder o1 with (nolock) WHERE o1.OrderDate BETWEEN '2008-1-1' AND '2009-1-1') AND o.BillEmail IN (SELECT DISTINCT o2.BillEmail FROM dbo.tblOrder o2 with (nolock) WHERE o2.OrderDate BETWEEN '2009-1-1' AND '2010-1-1') --AND o.OrderDate BETWEEN '2008-1-1' AND '2013-1-1' AND o.BillEmail NOT LIKE '%@halloweencostumes.com' AND o.BillEmail NOT LIKE '' GROUP BY YEAR(OrderDate) So I'm just finding the customers who purchased in both those years. And then I'm doing an independent query to find those who purchased in 2008 and 2010, then 08 and 11, and then 08 and 12. This one finds 2008 and 2010 purchasers: SELECT YEAR(OrderDate) as 'Year',COUNT(distinct(billemail)) as Customers FROM dbo.tblOrder o with (nolock) WHERE o.BillEmail IN (SELECT DISTINCT o1.BillEmail FROM dbo.tblOrder o1 with (nolock) WHERE o1.OrderDate BETWEEN '2008-1-1' AND '2009-1-1') AND o.BillEmail IN (SELECT DISTINCT o2.BillEmail FROM dbo.tblOrder o2 with (nolock) WHERE o2.OrderDate BETWEEN '2010-1-1' AND '2011-1-1') --AND o.OrderDate BETWEEN '2008-1-1' AND '2013-1-1' AND o.BillEmail NOT LIKE '%@halloweencostumes.com' AND o.BillEmail NOT LIKE '' GROUP BY YEAR(OrderDate) So you see I have a different query for each year comparison. They're all unrelated. So in the end I'm just finding people who bought in 2008 and 2009, and then a potentially different group that bought in 2008 and 2010, and so on. For this to be accurate, do I have to use the same grouping of 2008 buyers each time? So they bought in 2009 and 2010 and 2011, and 2012? This is where I'm worried and not sure how to proceed or even find such data. Any advice would be appreciated! Thanks!

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What's the difference between /123 and /?123?

- by BoltClock

I've noticed that some sites (including http://jobs.stackoverflow.com) have query strings that look like this: http://somewebapp.example/?123 as compared to: http://somewebapp.example/123 or http://somewebapp.example/id/123 What are the reasons that developers choose to implement their web apps' URLs using the first example instead of the second and third examples? And as a bonus, how would one implement the first example in PHP, given that 123 is the primary key of some row in a database table? (I just need to know how to retrieve 123 from the URL; I already know how to query the database for a primary key of 123.)

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Mysql Master Slave Replication on Large Database table (how to sync initial data)

- by Brian Lovett

We have a production server and a dev server. We have found that backups are nearly impossible on the production server because of the query volume we experience. So, we're looking at setting up replication with our dev server being the slave. This is ideal because we can afford to lock the tables on that server and additionally it will be nice to have up to date data for the developers. Now, the issues. The production server can't really be taken down or locked at this point, at least not easily. We have a high query volume and fairly large 30+ GB innodb tables. Both servers are running all innodb and are also both on mysql 5.1. What can we do to sync the data initially to get replication started? I've tried a few options, but so far, none have worked.

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Sphinx: change column set for searching in runtime

- by Fedyashev Nikita

I use Ultrasphinx gem plugin as a wrapper for accessing Sphinx search daemon. My model declaration: class Foo < ActiveRecord::Base is_indexed :fields => ['content', 'private_notes', 'user_id'] Client code: filters = {} if type == "private" # search only in `content` column filters['user_id'] = current_user.id else # search in `content` and `private_notes` columns end results = Ultrasphinx::Search.new(:query => params[:query], :per_page => 20, :page => params[:page] || 1, :filters => filters) The problem I have now with Ultrasphinx gem(or Sphinx, in general?) is that it does not allow me to change set of fields where to look for matches IN RUNTIME How can I solve this problem?

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detecting returned errors with $.post

- by sova

I'm using $.post to send a query to a JSP which returns some awesome data for me. If the query is malformed, however, the page returns with "error on page" and an HTTP Status of 500 Internal Server Error in jQuery, how can I detect this error so I can tell the user of the failure? runQuery : function () { $.post( admin_stats.runQueryURL, { buster : Math.random, statsQuery: admin_stats.getQuery(), jsp: 'admin_statsQuery' }, admin_stats.handleStatsQuery, "html" ); the returned data is an HTML table which is sufficient for this project at the moment. Also: totally open to criticism if this is ugly or not the way I should be doing things =)

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Renamed MySQL table not renamed for INSERT queries?

- by Austin Hyde

After renaming one of my MySQL MyISAM tables from test_tablename to tablename, I have found that if I try to execute an INSERT (or REPLACE) query, I get the following message: 1146: Table 'dbname.test_tablename' doesn't exist I have triple-checked my database abstraction code, and verified this by running the query directly on the server. According to the MySQL server, the CREATE TABLE syntax is tablename, as expected, and when I run SHOW TABLES, it lists tablename as expected. Is there any reason for this to happen? More importantly, is there an easier way to fix this than dumping, dropping, re-creating, and reloading the table?

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Changing Dropdown based on Other Dropdown Menu

- by Shaded

I've seen a few questions like this, but mine is a bit more specific so I hope this isn't considered a repost. I am working on a website that is built with struts 2 and hibernate. I need to dynamically populate a drop down menu using data from a sql query based on an option selected in another drop down menu. So basically when the first option is selected I need to rehit the server and get the results from a query like SELECT column FROM table WHERE option = dropDownOption On top of that, I would really like to use ajax to only refresh the affected elements, however I'm really unfamiliar with ajax. I have jquery on this project and I found they have some ajax built in, but is this a good method for using it? any advice on this topic would be appreciated.

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jquery update div as text input is modified

- by Piero

Hi, So I have this text input in a form, and I want to update a div as the user types text in the text input. <p><label for="movie_name">Film: </label> <input type="text" name="movie_name" class="required" onkeydown="changediv2(this.value)" /></p> <p><div id="ajax_update"></div></p> My js method: function changediv2(str) { $('#ajax_update').html(geturl('http://url/search/movie?query='+str)); } If I type in a browser http://url/search/movie?query=someString, I get some html displayed. But when I call it via this ajax call, nothing happens... My geturl method: function geturl(addr) { var r = $.ajax({ type: 'GET', url: addr, async: false }).responseText; return r; } I cannot see what is wrong in there... Please help me! :)

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how to configure hibernate not to update @Version on each access to entity

- by radai

i have a simple query that returns an entity, and when i look at hibernate SQL output i see that when i execute this query hibernate updates the @Version field (on each consecutive read the @version field is updated). i dont modify anything in the entity i fetch, and i dont pass is as an argument to either persist or merge. this effectively means every read i make turns into a read+write. i've tried setting the lock mode t oboth NONE (jpa 2) and READ (jpa 1) to no avail. is there any way to achieve this? if so, is there any way to set this as the default behavior in persistence.xml in some way ? im using jpa2 over hibernate 3.6

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Correct handling of return data

- by Serhiy

Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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Oracle - pl sql selecting from SYS_REFCURSOR

- by Einstein

I have a function that returns a SYS_REFCURSOR that has a single row but multiple columns. What I'm looking to do is to be able to have a SQL query that has nested sub-queries using the column values returned in the SYS_REFCURSOR. Alternative ideas such as types, etc would be appreciated. Code below is me writing on-the-fly and hasn't been validated for syntax. --Oracle function CREATE DummyFunction(dummyValue AS NUMBER) RETURN SYS_REFCURSOR IS RETURN_DATA SYS_REFCURSOR; BEGIN OPEN RETURN_DATA SELECT TO_CHAR(dummyValue) || 'A' AS ColumnA ,TO_CHAR(dummyValue) || 'B' AS ColumnB FROM DUAL; RETURN RETURN_DATA; END; --sample query with sub-queries; does not work SELECT SELECT ColumnA FROM DummyFunction(1) FROM DUAL AS ColumnA ,SELECT ColumnB FROM DummyFunction(1) FROM DUAL AS ColumnB FROM DUAL;

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Reduce the number of queries in EF

- by Gio2k

I have the following Model: Entities: Product (Contains basic data for products: price, etc) Attribute (Contains data for all possible optional attributes) ProductAttribute (Contains data for optional attributes of a product, eg. Color, Model, Size). ProductAttribute is essentially a many to many relationship with payload (ProductId, AttributeID, Value) And this piece of code: private static void ListAttributes(Product p) { p.ProductAttributes.Load(); foreach (var att in p.ProductAttributes) { att.Attribute.load(); Console.WriteLine("\tAttribute Name:{0} - Value {1}", att.Attribute.Name, att.AttributeValue); } } This piece of code will fire a query for each time the att.Attribute.Load() method is called in the foreach loop, only so i can get display the name of the attribute. I would like to fetch the Attribute.Name together with the query that fetches all attribute values, i.e. join ProductAttribute and Attribute. Is there any way to achieve this within my method?

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