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• SQL deadlock on delete then bulk insert

  - by StarLite

  I have an issue with a deadlock in SQL Server that I haven't been able to resolve. Basically I have a large number of concurrent connections (from many machines) that are executing transactions where they first delete a range of entries and then re-insert entries within the same range with a bulk insert. Essentially, the transaction looks like this BEGIN TRANSACTION T1 DELETE FROM [TableName] WITH( XLOCK HOLDLOCK ) WHERE [Id]=@Id AND [SubId]=@SubId INSERT BULK [TableName] ( [Id] Int , [SubId] Int , [Text] VarChar(max) COLLATE SQL_Latin1_General_CP1_CI_AS ) WITH(CHECK_CONSTRAINTS, FIRE_TRIGGERS) COMMIT TRANSACTION T1 The bulk insert only inserts items matching the Id and SubId of the deletion in the same transaction. Furthermore, these Id and SubId entries should never overlap. When I have enough concurrent transaction of this form, I start to see a significant number of deadlocks between these statements. I added the locking hints XLOCK HOLDLOCK to attempt to deal with the issue, but they don't seem to be helpling. The canonical deadlock graph for this error shows: Connection 1: Holds RangeX-X on PK_TableName Holds IX Page lock on the table Requesting X Page lock on the table Connection 2: Holds IX Page lock on the table Requests RangeX-X lock on the table What do I need to do in order to ensure that these deadlocks don't occur. I have been doing some reading on the RangeX-X locks and I'm not sure I fully understand what is going on with these. Do I have any options short of locking the entire table here?

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• SQL SELECT: "Give me all documents where all of the documents procedures are 'work in progress'"

  - by prestonmarshall

  This one really has me stumped. I have a documents table which hold info about the documents, and a procedures table, which is kind of like a revisions table for each document. What I need to do is write a select statement which gives me all of the documents where all of the procedures have the status "work_in_progress". Here's an example procedures table: document_id | status 1 | 'wip' 1 | 'wip' 1 | 'wip' 1 | 'approved' 2 | 'wip' 2 | 'wip' 2 | 'wip' Here, I would want my query to only return document id 2, because all of its statuses are work_in_progress. I DO NOT want document_id 1 since one of its statuses is 'approved'. I believe this is relational division I want, but I'm not sure where to start. This is MySQL 5.0 FYI.

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• Sequel Migration not running up?

  - by Sleepycat

  Having some trouble with the Migrations in Sequel and could use another set of eyes. I am running a migration that looks ok but no table is created. It is definitely connecting because I can see the schema_info table has been created. -M 0/1 changes the version as you would expect but still no table. The command: sequel -m . -M 1 ~/Desktop/dbtest/testdb.yml 001_testdb.rb: class TestDb < Sequel::Migration def up create_table( "terminals") do primary_key :id Integer :location_id Integer :merchant_id BigDecimal :terminal_id, :size=>[11, 0] String :reference, :size=>255 DateTime :created_at DateTime :updated_at String :image, :default=>"default.jpg", :size=>255 end end def down drop_table :terminals end end The output in Postgres: test_db=# \dt List of relations Schema | Name | Type | Owner --------+-------------+-------+---------- public | schema_info | table | postgres (1 row) test_db=# select * from schema_info; version --------- 1 (1 row)

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• Can you notice what's wrong with my PHP or MYSQL code?

  - by Jenna

  I am trying to create a category menu with sub categories. I have the following MySQL table: -- -- Table structure for table `categories` -- CREATE TABLE IF NOT EXISTS `categories` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(1000) NOT NULL, `slug` varchar(1000) NOT NULL, `parent` int(11) NOT NULL, `type` varchar(255) NOT NULL, PRIMARY KEY (`ID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=66 ; -- -- Dumping data for table `categories` -- INSERT INTO `categories` (`ID`, `name`, `slug`, `parent`, `type`) VALUES (63, 'Party', '/category/party/', 0, ''), (62, 'Kitchen', '/category/kitchen/', 61, 'sub'), (59, 'Animals', '/category/animals/', 0, ''), (64, 'Pets', '/category/pets/', 59, 'sub'), (61, 'Rooms', '/category/rooms/', 0, ''), (65, 'Zoo Creatures', '/category/zoo-creatures/', 59, 'sub'); And the following PHP: <?php include("connect.php"); echo "<ul>"; $query = mysql_query("SELECT * FROM categories"); while ($row = mysql_fetch_assoc($query)) { $catId = $row['id']; $catName = $row['name']; $catSlug = $row['slug']; $parent = $row['parent']; $type = $row['type']; if ($type == "sub") { $select = mysql_query("SELECT name FROM categories WHERE ID = $parent"); while ($row = mysql_fetch_assoc($select)) { $parentName = $row['name']; } echo "<li>$parentName >> $catName</li>"; } else if ($type == "") { echo "<li>$catName</li>"; } } echo "</ul>"; ?> Now Here's the Problem, It displays this: * Party * Rooms >> Kitchen * Animals * Animals >> Pets * Rooms * Animals >> Zoo Creatures I want it to display this: * Party * Rooms >> Kitchen * Animals >> Pets >> Zoo Creatures Is there something wrong with my loop? I just can't figure it out.

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• [Newbie] How to join mysql tables

  - by Ivan

  I've an old table like this: user> id | name | address | comments And now I've to create an "alias" table to allow some users to have an alias name for some reasons. I've created a new table 'user_alias' like this: user_alias> name | user But now I have a problem due my poor SQL level... How to join both tables to generate something like this: 1 | my_name | my_address | my_comments 1 | my_alias | my_address | my_comments 2 | other_name | other_address | other_comments I mean, I want to make a "SELECT..." query that returns in the same format as the "user" table ALL users and ALL alias.. Something like this: SELECT user.* FROM user LEFT JOIN user_alias ON `user`=`id` but it doesn't work for me..

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• Query doesn't use a covering-index when applicable

  - by Dor

  I've downloaded the employees database and executed some queries for benchmarking purposes. Then I noticed that one query didn't use a covering index, although there was a corresponding index that I created earlier. Only when I added a FORCE INDEX clause to the query, it used a covering index. I've uploaded two files, one is the executed SQL queries and the other is the results. Can you tell why the query uses a covering-index only when a FORCE INDEX clause is added? The EXPLAIN shows that in both cases, the index dept_no_from_date_idx is being used anyway. To adapt myself to the standards of SO, I'm also writing the content of the two files here: The SQL queries: USE employees; /* Creating an index for an index-covered query */ CREATE INDEX dept_no_from_date_idx ON dept_emp (dept_no, from_date); /* Show `dept_emp` table structure, indexes and generic data */ SHOW TABLE STATUS LIKE "dept_emp"; DESCRIBE dept_emp; SHOW KEYS IN dept_emp; /* The EXPLAIN shows that the subquery doesn't use a covering-index */ EXPLAIN SELECT SQL_NO_CACHE * FROM dept_emp INNER JOIN ( /* The subquery should use a covering index, but isn't */ SELECT SQL_NO_CACHE emp_no, dept_no FROM dept_emp WHERE dept_no="d001" ORDER BY from_date DESC LIMIT 20000,50 ) AS `der` USING (`emp_no`, `dept_no`); /* The EXPLAIN shows that the subquery DOES use a covering-index, thanks to the FORCE INDEX clause */ EXPLAIN SELECT SQL_NO_CACHE * FROM dept_emp INNER JOIN ( /* The subquery use a covering index */ SELECT SQL_NO_CACHE emp_no, dept_no FROM dept_emp FORCE INDEX(dept_no_from_date_idx) WHERE dept_no="d001" ORDER BY from_date DESC LIMIT 20000,50 ) AS `der` USING (`emp_no`, `dept_no`); The results: -------------- /* Creating an index for an index-covered query */ CREATE INDEX dept_no_from_date_idx ON dept_emp (dept_no, from_date) -------------- Query OK, 331603 rows affected (33.95 sec) Records: 331603 Duplicates: 0 Warnings: 0 -------------- /* Show `dept_emp` table structure, indexes and generic data */ SHOW TABLE STATUS LIKE "dept_emp" -------------- +----------+--------+---------+------------+--------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+ | Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment | +----------+--------+---------+------------+--------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+ | dept_emp | InnoDB | 10 | Compact | 331883 | 36 | 12075008 | 0 | 21544960 | 29360128 | NULL | 2010-05-04 13:07:49 | NULL | NULL | utf8_general_ci | NULL | | | +----------+--------+---------+------------+--------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+ 1 row in set (0.47 sec) -------------- DESCRIBE dept_emp -------------- +-----------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+---------+------+-----+---------+-------+ | emp_no | int(11) | NO | PRI | NULL | | | dept_no | char(4) | NO | PRI | NULL | | | from_date | date | NO | | NULL | | | to_date | date | NO | | NULL | | +-----------+---------+------+-----+---------+-------+ 4 rows in set (0.05 sec) -------------- SHOW KEYS IN dept_emp -------------- +----------+------------+-----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | +----------+------------+-----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ | dept_emp | 0 | PRIMARY | 1 | emp_no | A | 331883 | NULL | NULL | | BTREE | | | dept_emp | 0 | PRIMARY | 2 | dept_no | A | 331883 | NULL | NULL | | BTREE | | | dept_emp | 1 | emp_no | 1 | emp_no | A | 331883 | NULL | NULL | | BTREE | | | dept_emp | 1 | dept_no | 1 | dept_no | A | 7 | NULL | NULL | | BTREE | | | dept_emp | 1 | dept_no_from_date_idx | 1 | dept_no | A | 13 | NULL | NULL | | BTREE | | | dept_emp | 1 | dept_no_from_date_idx | 2 | from_date | A | 165941 | NULL | NULL | | BTREE | | +----------+------------+-----------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 6 rows in set (0.23 sec) -------------- /* The EXPLAIN shows that the subquery doesn't use a covering-index */ EXPLAIN SELECT SQL_NO_CACHE * FROM dept_emp INNER JOIN ( /* The subquery should use a covering index, but isn't */ SELECT SQL_NO_CACHE emp_no, dept_no FROM dept_emp WHERE dept_no="d001" ORDER BY from_date DESC LIMIT 20000,50 ) AS `der` USING (`emp_no`, `dept_no`) -------------- +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+-------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 50 | | | 1 | PRIMARY | dept_emp | eq_ref | PRIMARY,emp_no,dept_no,dept_no_from_date_idx | PRIMARY | 16 | der.emp_no,der.dept_no | 1 | | | 2 | DERIVED | dept_emp | ref | dept_no,dept_no_from_date_idx | dept_no_from_date_idx | 12 | | 21402 | Using where | +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+-------------+ 3 rows in set (0.09 sec) -------------- /* The EXPLAIN shows that the subquery DOES use a covering-index, thanks to the FORCE INDEX clause */ EXPLAIN SELECT SQL_NO_CACHE * FROM dept_emp INNER JOIN ( /* The subquery use a covering index */ SELECT SQL_NO_CACHE emp_no, dept_no FROM dept_emp FORCE INDEX(dept_no_from_date_idx) WHERE dept_no="d001" ORDER BY from_date DESC LIMIT 20000,50 ) AS `der` USING (`emp_no`, `dept_no`) -------------- +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+--------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+--------------------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 50 | | | 1 | PRIMARY | dept_emp | eq_ref | PRIMARY,emp_no,dept_no,dept_no_from_date_idx | PRIMARY | 16 | der.emp_no,der.dept_no | 1 | | | 2 | DERIVED | dept_emp | ref | dept_no_from_date_idx | dept_no_from_date_idx | 12 | | 37468 | Using where; Using index | +----+-------------+------------+--------+----------------------------------------------+-----------------------+---------+------------------------+-------+--------------------------+ 3 rows in set (0.05 sec) Bye

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• Making rows in to colums using sql query

  - by vaibhav

  I have a temp table in which have one coloum with four rows. Table ------ vaibhav IBM 12 'T' I need a temp table Col1 Col2 Col3 Col4 ------ ----- ----- ------ Vaibhav IBM 12 'T' Do anyone have any idea.

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• Duplicate entries on mysql on insert using doctrine

  - by Nikos Galis

  Hi all! I am facing a very weird problem with mysql and doctrine [with help of codeIgniter]. I am trying to make a simple migration script taking all records from one table and after a little process, saving them to another. However, on my laptop [running windows and wamp] I get double numbers of the original table records to have been copied to the destination table. In my colleagues' laptops, everything works fine! We are all using mysql 5.0.86 [plus windows plus wamp]. Here is the code : function buggy_function(){ $this->db(); //get db connection $q = Doctrine_Query::create()->from('Oldtable r'); $oldrecords = $q->fetchArray(); $count = 0; foreach ($oldrecords as $oldrecord){ $newrecord = new NewTableClass(); $newrecord->password = md5($oldrecord['password']); $newrecord->save(); echo $newrecord->id. ' Id -> saved.' } } Simple as that! I have 39 records on the Old table and I am getting 78 records in the new table, which are exactly the same records, except from the unique primary key. It seems as if the script runs twice. But the output of the script is the following : 1 Id -> saved. 2 Id -> saved. ... ... 39 Id -> saved. Do you have any idea why this is happening? Any known bug for mysql? Thank you in advanced!'

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• Why isn't my UITableView in a popover appearing in the correct scroll position?

  - by zbrimhall

  I have a split view-based app that presents a master-detail interface, and uses a popover to present the master list when in portrait mode. The popover presents a sectioned table view that ultimately gets populated by a subclass of NSFetchedResultsController. I can tap the tool bar button to present the master list, scroll to whatever row, and tap the row to dismiss the popover. My problem is that if the table is scrolled past the top of the second section, when I dismiss the popover and then later tap the toolbar button to re-present it, the table's scroll position is always set such that the first row of the second section is at the top of the list. If I haven't scrolled past the top of the second section, it correctly remembers its scroll position when the table is presented again. Similarly, in landscape mode, if I scroll the table past the top of the third section and then rotate to portrait, when I come back to landscape the scroll position is always set such that the first row of the third section is at the top of the list. I tried calling -scrollToNearestSelectedRowAtScrollPosition:animated in both the master view controller's -viewWillAppear, as well as in the split view delegate's splitViewController:popoverController:willPresentViewController:, to no effect. Anybody have a clue what I might be doing wrong?

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• Best practice to pass a value from pop over control on iPad.

  - by Tattat

  It is an iPad app based on SDK 3.2. I have a MainUIView, that is subclass from UIView, it have a UIButton and a UILabel. When user press the UIButton, the pop over control will be appeared with a table view. When the user select a cell from the table view, the UILabel changes content base on the user click, and the pop up table view will disappear. The question is, how can I pass the "selected cell" to the UILabel. I am thinking making a "middle man" object. When the user click the UIButton, and the "middle man" will pass to the table. When the cell is selected, the "middle man" will store the idx, and call the UILabel change content from the value of "middle man". But I think it is pretty complex to implement, is there any easier way to implement it? thz u.

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• Need help with Xpath methods in javascript (selectSingleNode, selectNodes)

  - by Andrija

  I want to optimize my javascript but I ran into a bit of trouble. I'm using XSLT transformation and the basic idea is to get a part of the XML and subquery it so the calls are faster and less expensive. This is a part of the XML: <suite> <table id="spis" runat="client"> <rows> <row id="spis_1"> <dispatch>'2008', '288627'</dispatch> <data col="urGod"> <title>2008</title> <description>Ur. god.</description> </data> <data col="rbr"> <title>288627</title> <description>Rbr.</description> </data> ... </rows> </table> </suite> In the page, this is the javascript that works with this: // this is my global variable for getting the elements so I just get the most // I can in one call elemCollection = iDom3.Table.all["spis"].XML.DOM.selectNodes("/suite/table/rows/row").context; //then I have the method that uses this by getting the subresults from elemCollection //rest of the method isn't interesting, only the selectNodes call _buildResults = function (){ var _RowList = elemCollection.selectNodes("/data[@col = 'urGod']/title"); var tmpResult = ['']; var substringResult=""; for (i=0; i<_RowList.length; i++) { tmpResult.push(_RowList[i].text,iDom3.Global.Delimiter); } ... //this variant works elemCollection = iDom3.Table.all["spis"].XML.DOM _buildResults = function (){ var _RowList = elemCollection.selectNodes("/suite/table/rows/row/data[@col = 'urGod']/title"); var tmpResult = ['']; var substringResult=""; for (i=0; i<_RowList.length; i++) { tmpResult.push(_RowList[i].text,iDom3.Global.Delimiter); } ... The problem is, I can't find a way to use the subresults to get what I need.

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• Searching 2 fields at the same time

  - by donpal

  I have a table of first and last names firstname lastname --------- --------- Joe Robertson Sally Robert Jim Green Sandra Jordan I'm trying to search this table based on an input that consists of the full name. For example: input: Joe Robert I thought about using SELECT * FROM tablename WHERE firstname LIKE BUT the table stores the first and last name separately, so I'm not sure how to do the search in this case

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• Database Design Primay Key, ID vs String

  - by LnDCobra

  Hi, I am currently planning to develop a music streaming application. And i am wondering what would be better as a primary key in my tables on the server. An ID int or a Unique String. Methods 1: Songs Table: SongID(int), Title(string), Artist*(string), Length(int), Album*(string) Genre Table Genre(string), Name(string) SongGenre: SongID*(int), Genre*(string) Method 2 Songs Table: SongID(int), Title(string), ArtistID*(int), Length(int), AlbumID*(int) Genre Table GenreID(int), Name(string) SongGenre: SongID*(int), GenreID*(int) Key: Bold = Primary Key, Field* = Foreign Key I'm currently designing using method 2 as I believe it will speed up lookup performance and use less space as an int takes a lot less space then a string. Is there any reason this isn't a good idea? Is there anything I should be aware of?

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• UIView Controller mysteriously getting deallocated

  - by Dan Ray

  I have a UINavigation scheme with a "welcome" page, a middle page, and a detail page. In the middle page, there's a segmented controller that can swap the main body of that page between a table, a calendar, and a MKMapView, each implemented with their own view controller classes. Today I implemented the MapView and its annotations and all of that. It's nice. And a detail disclosure on each callout takes you to the detail page just the same way as if you'd gotten there via the table. Lovely. I also have a right-button-bar button that pushes in a "search" view. From there you can search the data I'm navigating. When it's done filtering the data (an array of objects I'm keeping in a data singleton), it makes the table reload its data, and calls my annotation-clearer-and-builder methods on the map view, and then pops itself out, so the "middle" page (including whatever view was in the guts of it) is back on the screen. Problem is, if I go back and forth between the map and the search a couple times, any mention of the table view causes us to crash with: *** -[CALayer retain]: message sent to deallocated instance 0x710b810. (I obviously have NSZombies turned on.) I put an NSLog in the dealloc method of my table view controller. That thing's never getting called. I don't know if we're ditching it behind the scenes for memory purposes, or if I'm leaking it and can't get my hands back on it, or what. I'm sort of at a loss about where to look. Any hints?

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• If I'm updating a DataRow, do I lock the entire DataTable or just the DataRow?

  - by Dan Tao

  Suppose I'm accessing a DataTable from multiple threads. If I want to access a particular row, I suspect I need to lock that operation (I could be mistaken about this, but at least I know this way I'm safe): // this is a strongly-typed table OrdersRow row = null; lock (orderTable.Rows.SyncRoot) { row = orderTable.FindByOrderId(myOrderId); } But then, if I want to update that row, should I lock the table (or rather, the table's Rows.SyncRoot object) again, or can I simply lock the row?

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• fast retrieval from MYSQL DB

  - by trojanwarrior3000

  I have a table of users - It contains around millions of rows (user-id is the primary key). I just want to retrieve user-id and their joining date. using "select user-id,joining date from table user" requires lot of time.Is there a fast way to query/retrieve the same data from this table?

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• Datamodel for a MVC learning project

  - by Dofs

  Hi, I am trying to learn Microsoft MVC 2, and have in that case found a small project I wanted to deploy it on. My idea was to simulate a restaurant where you can order a table. Basics: A user can only reserve a full table, so I don't have the trouble of merging people on different tables. A person can order a table for a certain amount of hours. My question was how I could make the data model the smartest way. I thought of just having a my database like this: Table { Id, TableName } Reservations { Id TableId ReservedFrom ReservedTo UserId } User { UserId UserName ... } By doing it this way I would have to program a lot of the logic in e.g. the business layer, to support which tables are occupied at what time, instead of having the data model handle it. Therefore do you guys have a better way to do this?

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• Strategy in exporting to Excel with formatting from ASP.NET?

  - by Jiho Han

  So this is another exporting to Excel question. I have a page that has a table with formatting by stylesheet. When I export the page by setting the ContentType to application/excel and Content-Disposition to attachment, I can export the table to Excel (not CSV). However, it loses all formatting. I think it's because Excel does not load CSS and I guess that's reasonable. So, in a scenario where I have to show the table on the web and also export to Excel, both with similar (even if not exact) formatting, what would be the best approach without using something like NPOI? I am trying to minimize the work and keep the single template if possible. Is it necessary for me to create two separate templates: one with stylesheet, the other with embedded style in the table itself for Excel? Having a single template with conditional formatting inside would be very messy. Any ideas?

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• Using hash tables in racket

  - by user2963128

  Im working on an Ngrams program and im having trouble filling out my hash table. i want to write out a recursive function that will take the words and add them to the hash table. The way its supposed to work is given the data set 1 2 3 4 5 6 7 the first entry in the hash table should have a key of [1 2] and the data should be 3. The second entry should be: [2 3] and its data should be 4 and continuing on until the end of the text file. we are given a predefined function called readword that will simply return 1 word from the text. But im not sure how to make these calls overlap each other. The calls would look something like this if the data was hard coded in. (hash-set! (list "1" "2") 3 (hash-set! (list "2" "3") 4 2 calls that ive tried look like this (hash-set! Ngram-table(list((word1) (word2)) readword in))) (hash-set! Ngram-table(append((cdr data) word1)) readword in) apparently the in after readword is supposed to tell the computer that this is and input instead of an output or something like that. How would I call this to make the data in the key of the hashtable overlap like this? And what would the recursive call look like? edit: also we are not allowed to use assigment statements in this program.

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• Hibernate - how to delete bidirectional many-to-many association

  - by slomir

  Problem: I have many-to-many association between two entities A and B. I set A entity as an owner of their relationship(inverse=true is on A's collection in b.hbm.xml). When i delete an A entity, corresponding records in join table are deleted. When i delete an B entity, corresponding records in join table are not deleted (integrity violation exception). -- Let's consider some very simple example: class A{ Set<B> bset=new HashSet<B>(); //... } class B{ Set<A> aset=new HashSet<A>(); //... } File a.hbm.xml [m-to-m mappings only]: <set name="bset" table="AB"> <key name="a_id"/> <many-to-many column="b_id" class="B"/> </set> File b.hbm.xml [m-to-m mappings only]: <set name="aset" table="AB" inverse="true"> <key name="b_id"/> <many-to-many column="a_id" class="A"/> </set> Database relations: A(id,...) B(id,...) AB(a_id,b_id) Suppose that we have some records in AB joint table. For example: AB = {(1,1),(1,2)} where AB= { (a_id , b_id) | ... ... } -- Situation 1 - works probably because A is owner of AB relationship: A a=aDao.read(1); //read A entity with id=1 aDao.delete(a); //delete 'a' entity and both relations with B-entities Situation 2 - doesn't work: B b=bDao.read(1); //read B entity with id=1 bDao.delete(b); //foreign key integrity violation On the one hand, this is somehow logical to me, because the A entity is responsible for his relation with B. But, on the other hand, it is not logical or at least it is not orm-like solution that I have to explicitly delete all records in join table where concrete B entity appears, and then to delete the B entity, as I show in situation 3: Situation 3 - works, but it is not 'elegant': B b=bDao.read(1); Set<A> aset=b.getA(); //get set with A entities Iterator i=aset.iterator(); //while removes 'b' from all related A entities //while breaks relationships on A-side of relation (A is owner) while(i.hasNext()){ A a=i.next(); a.bset.remove(b); //remove entity 'b' from related 'a' entity aDao.update(a); //key point!!! this line breaks relation in database } bDao.delete(b); //'b' is deleted because there is no related A-entities -- So, my question: is there any more convenient way to delete no-owner entity (B in my example) in bidirectional many-to-many association and all of his many-to-many relations from joint table?

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• I need to calculate the date / time difference between one date time column

  - by Stringz

  Details. I have the notes table having the following columns. ID - INT(3) Date - DateTime Note - VARCHAR(100) Tile - Varchar(100) UserName - Varchar(100) Now this table will be having NOTES along with the Titles entered by UserName on the specified date / time. I need to calculate the DateTimeDifference between the TWO ROWS in the SAME COLUMN For example the above table has this peice of information in the table. 64, '2010-03-26 18:16:13', 'Action History', 'sending to Level 2.', 'Salman Khwaja' 65, '2010-03-26 18:19:48', 'Assigned By', 'This is note one for the assignment of RF.', 'Salman Khwaja' 66, '2010-03-27 19:19:48', 'Assigned By', 'This is note one for the assignment of CRF.', 'Salman Khwaja' Now I need to have the following resultset in query reports using MYSQL. TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 00:03:35 Assigned By - 25:00:00 More smarter approach would be TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 3 minutes 35 seconds Assigned By - 1 day, 1 hour. I would appreciate if one could give me the PLAIN QUERY along with PHP code to embed it too.

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• How to assign .net membership roles to individual database records

  - by mdresser

  I'm developing a system where we want to restrict the availability of information displayed to users based on their roles. e.g. I have a tabled called EventType (ID, EventTypeDescription) which contains the following records: 1, 'Basic Event' 2, 'Intermediate Event' 3, 'Admin Event' What I need to achieve is to filter the records returned based on the username (and hence role) of the logged-in user. e.g if an advanced user is logged in they will see all the event types, if the standard user is logged in they will only see the basic event type etc. Ideally id like to do this in a way which can be easily extended to other tables as necessary. So I'd like to avoid simply adding a 'Roles' field to each table where the data is user context sensitive. One idea I'm thinking of is to create some kind of permissions table like: PermissionsTable ( ID, Aspnet_RoleId, TableName, PrimaryKeyValue ) this has the drawback of using this is obviously having to use the table name to switch which table to join onto. Edit: In the absence of any better suggestions, I'm going to go with the last idea I mentioned, but instead of having a TableName field, I'm going to normalise the TableName out to it's own table as follows: TableNames ( ID, TableName ) UserPermissionsTable ( ID, Aspnet_UserId, TableID, PrimaryKeyValue )

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• Push a ViewController and It Pops Right Back

  - by Jim Bonner

  I have a view controller with a table view and a UISearchBar. When the view controller is first brought up, the table is populated. A click on a table row pushes another view controller, it animates up and then pops right back down and returns me to the table. It does this whether the search bar has been used or not. I do this push pop kind of action in several view controllers with not problem. My guess is that the UISearchBar is somehow getting in the way. Any one have any idea as to what I'm doing wrong?

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• Recording SELECT statements in PostgreSQL 8.4

  - by David Anniwell

  Hi All I've got a table which contains sensitive data and according to data protection policy we have to keep a record of every read/write of the data including a row identifier and the user who accessed the table. The writing is no issue using triggers but obviously triggers aren't supported for SELECT statements. What's the best method of doing this? I've looked at rules but I can't get them to INSERT into a table, and I've tried logging every query but this doesn't seem to log SELECT statements. Ideally for security I'd like to keep the log within a table on the database but logging to a file is fine too. Thanks David

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• does it makes sense to use int instead of char or nvarchar for a discriminator column if I'm using i

  - by Omu

  I have something like this: create table account ( id int identity(1,1) primary key, usertype char(1) check(usertype in ('a', 'b')) not null, unique(id, usertype) ) create table auser ( id int primary key, usertype char(1) check(usertype = 'a') not null, foreign key (id, usertype) references account(id, usertype) ) create table buser ( ... same just with b ) the question is: if I'm going to use int instead of char(1), does it going to work faster/better ?

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