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  • Query table value aliasing in Oracle SQL

    - by Strata
    I have a homework assignment in SQL for Oracle 10g where I have to apply union to two different select statements, to return two columns. I need the values of each cell under vendor_state to indicate CA and every other value in another state to return "Outside CA", to indicate they're elsewhere. I applied the union and produced the two columns and the listings for CA, but many other state IDs were listed and I couldn't find an explanation for how to change the actual values in the query itself. Eventually, I stumbled on an answer, but I can't explain why this works. The code is as follows: SELECT vendor_name, vendor_state FROM vendors WHERE vendor_state IN 'CA' UNION SELECT vendor_name, 'Outside CA' AS vendor_state FROM vendors WHERE vendor_state NOT IN 'CA' ORDER BY vendor_name This gives me the exact answer I need, but I don't know why the aliasing in the second select statement can behave this way....no explanation is given in my textbook and nothing I've read indicates that column aliasing can be done like this. But, by switching the column name and the alias value, I have replaced the value being returned rather than the column name itself...I'm not complaining about the result, but it would help if I knew how I did it.

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  • wanted to get all dates in mysql result

    - by PankajK
    I have mysql table called user(id, name, join_on) join on is a date field what I want is to show in each day how many uses has been created I can use group by but it will only give me the dates when users get added like if date 4/12/10 5 users added 4/13/10 2 users added 4/15/10 7 users added here date 4/14/10 is missing and I want listing of all dates in one month. I have one solution for it by creating another table only for adding date and that table will left join my users table on join_on and will give total result but I don't want to do that as for creating that I need to create and add entries in date table please suggest the different approach for doing so. Thank you.

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  • mysql_num_rows(): supplied argument is not a valid MySQL result resource

    - by php-b-grader
    I am getting this error when I pass an invalid SQL string... I spent the last hour trying to find the problem assuming - It's not my SQL it must be the db handle... ANyway, I've now figured out that it was bad SQL... What I want to do is test the result of the mysql_query() for a valid resultset. I am simply using empty($result)... Is this the most effective test? Is there a more widely accepted method of testing a resultset for a valid result?

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  • SQL: Optimize insensive SELECTs on DateTime fields

    - by Fedyashev Nikita
    I have an application for scheduling certain events. And all these events must be reviewed after each scheduled time. So basically we have 3 tables: items(id, name) scheduled_items(id, item_id, execute_at - datetime) - item_id column has an index option. reviewed_items(id, item_id, created_at - datetime) - item_id column has an index option. So core function of the application is "give me any items(which are not yet reviewed) for the actual moment". How can I optimize this solution for speed(because it is very core business feature and not micro optimization)? I suppose that adding index to the datetime fields doesn't make any sense because the cardinality or uniqueness on that fields are very high and index won't give any(?) speed-up. Is it correct? What would you recommend? Should I try no-SQL? -- mysql -V 5.075 I use caching where it makes sence.

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  • VS2008 is very slow on a specific large C++ solution

    - by VioletRose
    I have a solution with 21 C++ projects and 1 VB.NET project. The IDE responds very slowly when I simply move the carret in a file or try to open the menu. The process seems to take 50% of CPU for each movement. It only happens with this solution and only on my machine. The solution has total of 2380 source and header files, of which 1280 are header files. I tried to remove all connection to the source control (Perforce) but it didn't help. Also, I have Visual Assist installed but even after removing it (uninstall), the same behavior continued. Any idea?

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  • Is it possible to put a form control on its own thread?

    - by BVernon
    I'm using a DataGridView and some operations that I do cause it to become unresponsive for periods of time. Normally I would put data processing in its own thread to make the form more responsive, but in this case it's the DataGridView itself that's taking so long. This leads me to wonder whether it's possible to have the main form on one thread and the DataGridView on another thread so it doesn't prevent the main form from responding. I completely understand that doing so is probably not 'safe' and likely opens up a can of worms that makes it hardly worth trying and I fully expect this post will be getting down votes for merely suggesting such a ridiculous idea. Is this possible? And if so how would you go about it?

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  • Updating multiple rows with an array

    - by Copephobia
    I have a table that holds user information. One of the columns holds the position of the user in the game they are in. When a game is being created, I need to update the positions of the users of each team. Here is an example: Game id : 7 Team 1 users : 1,2 Team 2 users : 3,4 team1_position : array(1,2) team2_position : array(13,14) What I want to do is update the user table using the array of positions in the SET area. My goal is to be able to update the users without the need for their id (I have different size game boards, so I have multiple position arrays for each board size) How can I do something like this: UPDATE user SET position='(team1_position)' WHERE game = '7' AND team = '1' I feel like it would be a waste of resources to select all the id's of each team and update them separately.

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  • Not sure how to use Decode, NVL, and/or isNull (or something else?) in this situation

    - by RSW
    I have a table of orders for particular products, and a table of products that are on sale. (It's not ideal database structure, but that's out of my control.) What I want to do is outer join the order table to the sale table via product number, but I don't want to include any particular data from the sale table, I just want a Y if the join exists or N if it doesn't in the output. Can anyone explain how I can do this in SQL? Thanks in advance!

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  • Best way to get distinct values from large table

    - by derivation
    I have a db table with about 10 or so columns, two of which are month and year. The table has about 250k rows now, and we expect it to grow by about 100-150k records a month. A lot of queries involve the month and year column (ex, all records from march 2010), and so we frequently need to get the available month and year combinations (ie do we have records for april 2010?). A coworker thinks that we should have a separate table from our main one that only contains the months and years we have data for. We only add records to our main table once a month, so it would just be a small update on the end of our scripts to add the new entry to this second table. This second table would be queried whenever we need to find the available month/year entries on the first table. This solution feels kludgy to me and a violation of DRY. What do you think is the correct way of solving this problem? Is there a better way than having two tables?

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  • C++ Function pointers vs Switch

    - by Perfix
    What is faster: Function pointers or switch? The switch statement would have around 30 cases, consisting of enumarated unsigned ints from 0 to 30. I could do the following: class myType { FunctionEnum func; string argv[123]; int someOtherValue; }; // In another file: myType current; // Iterate through a vector containing lots of myTypes // ... for ( i=0; i < myVecSize; i ++ ) switch ( current.func ) { case 1: //... break; // ........ case 30: // blah break; } And go trough the switch with func every time. The good thing about switch would also be that my code is more organized than with 30 functions. Or I could do that (not so sure with that): class myType { myReturnType (*func); string argv[123]; int someOtherValue; }; I'd have 30 different functions then, at the beginning a pointer to one of them is assigned to myType. What is probably faster: Switch statement or function pointer? Calls per second: Around 10 million. I can't just test it out - that would require me to rewrite the whole thing. Currently using switch. I'm building an interpreter which I want to be faster than Python & Ruby - every clock cycle matters!

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  • Find Consecutive Rows & Calculate Duration

    - by MannyKo
    I have a set a of data that tells me if a couple of systems are available or not every 5 or 15 minutes increments. For now, the time increment shouldn't matter. The data looks like this: Status Time System_ID T 10:00 S01 T 10:15 S01 F 10:30 S01 F 10:45 S01 F 11:00 S01 T 11:15 S01 T 11:30 S01 F 11:45 S01 F 12:00 S01 F 12:15 S01 T 12:30 S01 F 10:00 S02 F 10:15 S02 F 10:30 S02 F 10:45 S02 F 11:00 S02 T 11:15 S02 T 11:30 S02 I want to create a view that tells when a system is NOT available (i.e. when it is F), from what time, to what time, and duration which is to - from. Desired results: System_ID From To Duration S01 10:30 11:00 00:30 S01 11:45 12:15 00:30 S02 10:00 11:00 01:00 Here is the script data: DROP SCHEMA IF EXISTS Sys_data CASCADE; CREATE SCHEMA Sys_data; CREATE TABLE test_data ( status BOOLEAN, dTime TIME, sys_ID VARCHAR(10), PRIMARY KEY (dTime, sys_ID) ); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '10:00:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '10:15:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:30:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:45:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '11:00:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '11:15:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '11:30:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '11:45:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '12:00:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '12:15:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '12:30:00', 'S01'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:00:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:15:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:30:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '10:45:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (FALSE, '11:00:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '11:15:00', 'S02'); INSERT INTO test_data (status, dTime, sys_ID) VALUES (TRUE, '11:30:00', 'S02'); Thank you in advance!

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  • MySQL, how to use returned data?

    - by aejo
    Well, I know there is a funciton mysql_fetch_array() and we can use it like this: while ($row = mysql_fetch_array($result)) { echo $row['name'] . "<br />"; } But is there any other way? For example, if there is only one element that can be returned, and not an array. Thanks)

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  • Why is Python so slow?

    - by Riemannliness
    Why is Python such a slow language, on average, compared to C/C++? I learned Python as my first programming language, but I've only just started with C and already I can feel and see the difference.

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  • how does array_diff work?

    - by SpawnCxy
    I just wonder how array_diff() works.And obviously it couldn't work as follows function array_diff($arraya, $arrayb) { $diffs = array(); foreach ($arraya as $keya => $valuea) { foreach ($arrayb as $valueb) { if ($valuea == $valueb) { break; } $diffs[$keya]=$valuea; } } return $diffs; } //couldn't be worse than this Hope someone can show me some better solution. Thanks.

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  • fast load big object graph from DB

    - by Famos
    Hi I have my own data structure written in C# like: public class ElectricScheme { public List<Element> Elements { get; set; } public List<Net> Nets { get; set; } } public class Element { public string IdName { get; set; } public string Func { get; set; } public string Name { get; set; } public BaseElementType Type { get; set; } public List<Pin> Pins { get; set; } } public class Pin { public string IdName { get; set; } public string Name { get; set; } public BasePinType PinType { get; set; } public BasePinDirection PinDirection { get; set; } } public class Net { public string IdName { get; set; } public string Name { get; set; } public List<Tuple<Element,Pin>> ConnectionPoints { get; set; } } Where Elements count ~19000, each element contain =3 Pin, Nets count ~20000, each net contain =3 pair (Element, Pin) Parse txt (file size ~17mb) file takes 5 minutes. Serilization / Deserialization by default serializer ~3 minutes. Load from DB 20 minutes and not loaded... I use Entity Framework like public ElectricScheme LoadScheme(int schemeId) { var eScheme = (from s in container.ElectricSchemesSet where s.IdElectricScheme.Equals(schemeId) select s).FirstOrDefault(); if (eScheme == null) return null; container.LoadProperty(eScheme, "Elements"); container.LoadProperty(eScheme, "Nets"); container.LoadProperty(eScheme, "Elements.Pins"); return eScheme; } The problem is dependencies between Element and Pin... (for ~19000 elements ~95000 pins) Any ideas?

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  • Sorting MySQL table by next due date

    - by Zagga
    Hi folks, I have a MySQL table that stores (amongst other things) a persons date of birth. Is there any way to sort the table so the next due birthday is at the top? I have the date stored in standard yyyy-mm-dd DATE format and seperate year, month and day fields so I can sort it by the first birthday of the year (ORDER BY month, day) but I can't seem to get any further. Any help would be greatly appreciated. Zagga

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  • Fastest way to read/store lots of multidimensional data? (Java)

    - by RemiX
    I have three questions about three nested loops: for (int x=0; x<400; x++) { for (int y=0; y<300; y++) { for (int z=0; z<400; z++) { // compute and store value } } } And I need to store all computed values. My standard approach would be to use a 3D-array: values[x][y][z] = 1; // test value but this turns out to be slow: it takes 192 ms to complete this loop, where a single int-assignment int value = 1; // test value takes only 66 ms. 1) Why is an array so relatively slow? 2) And why does it get even slower when I put this in the inner loop: values[z][y][x] = 1; // (notice x and z switched) This takes more than 4 seconds! 3) Most importantly: Can I use a data structure that is as quick as the assignment of a single integer, but can store as much data as the 3D-array?

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  • Outer select column value in joined subquery?

    - by Michael DePetrillo
    Is it possible to use a column value from an outer select within a joined subquery? SELECT table1.id, table2.cnt FROM table1 LEFT JOIN (SELECT COUNT(*) as `cnt` FROM table2 where table2.lt > table1.lt and table2.rt < table1.rt) as table2 ON 1; This results in "Unknown column 'table1.lt' in 'where clause'". Here is the db dump. CREATE TABLE IF NOT EXISTS `table1` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; CREATE TABLE IF NOT EXISTS `table2` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `table1` (`id`, `lt`, `rt`) VALUES (1, 1, 4); INSERT INTO `table2` (`id`, `lt`, `rt`) VALUES (2, 2, 3);

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  • Android-SQLite: How to Count specific value from Column?

    - by sanpatil
    I have two table (TABLE_EXAM,TABLE_RESULT). Here is value of my TABLE_RESULT. result_id exam_id question_id correct_answer 1 2 4 y 2 2 5 y 3 2 6 n 4 2 7 y I need to count how many correct_answer='y' where exam_id=2. I try following code but it return 0. public int calculateResult(int examId,String confirmAnswer) { int correctAnswer=0; try { SQLiteDatabase db=this.getWritableDatabase(); String selectQuery=("select count(correctAnswer) from result where exam_id ='" + examId + "' and correctAnswer ='" + 'y' +"'" ); // String selectQuery=("SELECT COUNT(*)FROM result WHERE exam_id ='" + examId + "' and correctAnswer ='" + confirmAnswer +"'" ); Cursor cursor = db.rawQuery(selectQuery, null); if(cursor.moveToLast()) { correctAnswer=cursor.getInt(3); } } catch(Exception e) { e.printStackTrace(); } return correctAnswer; } In variable confirm_answer i pass "y". Give me some hint or reference. Any help is appreciated. Thanks in Advance

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  • Does beginTransaction in Hibernate allocate a new DB connection?

    - by illscience
    Hi folks - Just wondering if beginning a new transaction in Hibernate actually allocates a connection to the DB? I'm concerned b/c our server begins a new transaction for each request received, even if that request doesn't interact with the DB. We're seeing DB connections as a major bottleneck, so I'm wondering if I should take the time narrow the scope of my transactions. Searched everywhere and haven't been able to find a good answer. The very simple code is here: SessionFactory sessionFactory = (SessionFactory) Context.getContext().getBean("sessionFactory"); sessionFactory.getCurrentSession().beginTransaction(); sessionFactory.getCurrentSession().setFlushMode(FlushMode.AUTO); thanks very much! a

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  • PHP Try and Catch for SQL Insert

    - by meme
    I have a page on my website (high traffic) that does an insert on every page load. I am curious of the fastest and safest way to (catch an error) and continue if the system is not able to do the insert into MySQL. Should I use try/catch or die or something else. I want to make sure the insert happens but if for some reason it can't I want the page to continue to load anyway. ... $db = mysql_select_db('mobile', $conn); mysql_query("INSERT INTO redirects SET ua_string = '$ua_string'") or die('Error #10'); mysql_close($conn); ...

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