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  • Problem counting item frequency on T-SQL

    - by Raúl Roa
    I'm trying to count the frequency of numbers from 1 to 100 on different fields of a table. Let's say I have the table "Results" with the following data: LottoId Winner Second Third --------- --------- --------- --------- 1 1 2 3 2 1 2 3 I'd like to be able to get the frequency per numbers. For that I'm using the following code: --Creating numbers temp table CREATE TABLE #Numbers( Number int) --Inserting the numbers into the temp table declare @counter int set @counter = 0 while @counter < 100 begin set @counter = @counter + 1 INSERT INTO #Numbers(Number) VALUES(@counter) end -- SELECT #Numbers.Number, Count(Results.Winner) as Winner,Count(Results.Second) as Second, Count(Results.Third) as Third FROM #Numbers LEFT JOIN Results ON #Numbers.Number = Results.Winner OR #Numbers.Number = Results.Second OR #Numbers.Number = Results.Third GROUP BY #Numbers.Number The problem is that the counts are repeating the same values for each number. In this particular case I'm getting the following result: Number Winner Second Third --------- --------- --------- --------- 1 2 2 2 2 2 2 2 3 2 2 2 ... When I should get this: Number Winner Second Third --------- --------- --------- --------- 1 2 0 0 2 0 2 0 3 0 0 2 ... What am I missing?

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  • Cannot change borderColor of TD

    - by Tadeus Prastowo
    Using JS to set the background color of a TD is fine. But, setting the border color is problematic in FF 3.0.18 although IE 6 doesn't experience this. FF is problematic in that it requires the TD element to have an attribute style initialized to border-style: solid. Without that, setting border color of a TD won't work. Is this known bug? How do I set the border color without having to set style attribute as well as the initialization value? I know another trick of setting the class attribute instead of setting the border color directly. Is this an indication that somehow TD hates having its border color set dynamically? Is this known as well? The problematic code is below (the goal is find out why setting the border color of simple truth 1 does not work while simple truth 3 works when I employ the trick described above): <html> <head> <title>Quirks FF 3.0.18</title> <style type="text/css"> table { border-collapse: collapse; } </style> <script type="text/javascript"> function changeBgColor() { document.getElementById('simple').style.backgroundColor='yellow'; document.getElementById('simple2').style.backgroundColor='yellow'; document.getElementById('simple3').style.backgroundColor='yellow'; } function quirk(id) { var x = document.getElementById(id); x.style.border = '2px solid red'; } </script> </head> <body> <input type="button" onclick="changeBgColor()" value="Change background color"/> <input type="button" onclick="quirk('simple')" value="Change border color 1"/> <input type="button" onclick="quirk('simple2')" value="Change border color 2"/> <input type="button" onclick="quirk('simple3')" value="Change border color 3"/> <table> <tr><td id="simple">Simple truth 1</td></tr> </table> <table> <tr><td><span id="simple2">Simple truth 2</span></td></tr> <table> <tr><td id="simple3" style="border-style: solid">Simple truth 3</td></tr> </table> </body> </html>

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  • Generating the SQL query plan takes 5 minutes, the query itself runs in milliseconds. What's up?

    - by TheImirOfGroofunkistan
    I have a fairly complex (or ugly depending on how you look at it) stored procedure running on SQL Server 2008. It bases a lot of the logic on a view that has a pk table and a fk table. The fk table is left joined to the pk table slightly more than 30 times (the fk table has a poor design - it uses name value pairs that I need to flatten out. Unfortunately, it's 3rd party and I cannot change it). Anyway, it had been running fine for weeks until I periodically noticed a run that would take 3-5 minutes. It turns out that this is the time it takes to generate the query plan. Once the query plan exists and is cached, the stored procedure itself runs very efficiently. Things run smoothly until there is a reason to regenerate and cache the query plan again. Has anyone seen this? Why does it take so long to generate the plan? Are there ways to make it come up with a plan faster?

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  • Is there a code-generator to create DataTable definition block from Excel Work sheet?

    - by burak ozdogan
    Hi, Basically the thing I want to achieve is to have a data-table that I want to use in my unit tests. And when I run my unit tests, I do not want to read any excel file into a data-table -or any call to Db-. So, I would like to have method that returns a data-table with the values that I can use in my test. Is there already any written tool to read an excel sheet and generate a code that defines an ADO.Net DataTable? Thanks, burak ozdogan

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  • How to read a CLOB column in Oracle using OleDb ?

    - by T.Falise
    Hi, I have created a table on an Oracle 10g database with this structure : create table myTable ( id number(32,0) primary key, myData clob ) I can insert rows in the table without any problem, but when I try to read data from the table using OleDb connection, I get an exception. Here is the code I use : using (OleDbConnection dbConnection = new OleDbConnection("ConnectionString")) { dbConnection.Open(); OleDbCommand dbCommand = dbConnection.CreateCommand(); dbCommand.CommandText = "SELECT * FROM myTable WHERE id=?"; dbCommand.Parameters.AddWithValue("ID", id); OleDbDataReader dbReader = dbCommand.ExecuteReader(); } The exception details seems to point on an unsupported data type : System.Data.OleDb.OleDbException: Unspecified error Oracle error occurred, but error message could not be retrieved from Oracle. Data type is not supported. Does anyone know how I can read this data using the OleDb connection ? PS : The driver used in this case is the Microsoft one.

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  • SQLite - a smart way to remove and add new objects

    - by Ilya
    Hi, I have a table in my database and I want for each row in my table to have an unique id and to have the rows named sequently. For example: I have 10 rows, each has an id - starting from 0, ending at 9. When I remove a row from a table, lets say - row number 5, there occurs a "hole". And afterwards I add more data, but the "hole" is still there. It is important for me to know exact number of rows and to have at every row data in order to access my table arbitrarily. There is a way in sqlite to do it? Or do I have to manually manage removing and adding of data? Thank you in advance, Ilya.

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  • Optimize this MySQL query?

    - by HipHop-opatamus
    The following query takes FOREVER to execute (30+ hrs on a Macbook w/4gig ram) - I'm looking for ways to make it run more efficiently. Any thoughts are appreciated! CREATE TABLE fc AS SELECT threadid, title, body, date, userlogin FROM f WHERE pid NOT IN (SELECT pid FROM ft) ORDER BY date; (table "f" is ~1 Gig / 1,843,000 row, table "ft" is 168mb, 216,000 rows) )

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  • Data in two databases, eager spool resulting in query

    - by Valkyrie
    I have two databases in SQL2k5: one that holds a large amount of static data (SQL Database 1) (never updated but frequently inserted into) and one that holds relational data (SQL Database 2) related to the static data. They're separated mainly because of corporate guidelines and business requirements: assume for the following problem that combining them is not practical. There are places in SQLDB2 that PKs in SQLDB1 are referenced; triggers control the referential integrity, since cross-database relationships are troublesome in SQL Server. BUT, because of the large amount of data in SQLDB1, I'm getting eager spools on queries that join from the Id in SQLDB2 that references the data in SQLDB1. (With me so far? Maybe an example will help:) SELECT t.Id, t.Name, t2.Company FROM SQLDB1.table t INNER JOIN SQLDB2.table t2 ON t.Id = t2.FKId This query results in a eager spool that's 84% of the load of the query; the table in SQLDB1 has 35M rows, so it's completely choking this query. I can't create a view on the table in SQLDB1 and use that as my FK/index; it doesn't want me to create a constraint based on a view. Anyone have any idea how I can fix this huge bottleneck? (Short of putting the static data in the first db: believe me, I've argued that one until I'm blue in the face to no avail.) Thanks! valkyrie Edit: also can't create an indexed view because you can't put schemabinding on a view that references a table outside the database where the view resides. Dang it.

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  • MS SQL Return 1 Row Per Boat

    - by Tyler
    Basically, what I want to do is join 4 tables together and return 1 row for each boat. Table Layouts [Boats] id, date, section, raft [Photos] id, boatid, pthurl, purl [River_Company] id, sort, company, company_short [River_Section] id, section Its very simple as far as structure, however, I've having the time of my life trying to get it to return only 1 row. No boat will ever be on the same day, the only thing that's messing this up is the photo table. If you know a better way for it to return the record table for all the boats boats and only 1 photo from the photo table, please, please post it!!

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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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  • Selenium Testing

    - by Joakim
    Hi I want to get a bunch of dom-objects with xpath and loop through those to check if they contains a specified text, is this possible in the Selenium IDE or rc? Perl is my prefered language XPath would be something like xpath=//tbody[@class='table-data']/tr/td/div[@class='table-item'] This would return all row items in the table, but i need to check each div if contains a specified text string. Is this possible with Selenium? Best regards

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  • Android: database reading problem throws exception

    - by Vamsi
    Hi, i am having this problem with the android database. I adopted the DBAdapter file the NotepadAdv3 example from the google android page. DBAdapter.java public class DBAdapter { private static final String TAG = "DBAdapter"; private static final String DATABASE_NAME = "PasswordDb"; private static final String DATABASE_TABLE = "myuserdata"; private static final String DATABASE_USERKEY = "myuserkey"; private static final int DATABASE_VERSION = 2; public static final String KEY_USERKEY = "userkey"; public static final String KEY_TITLE = "title"; public static final String KEY_DATA = "data"; public static final String KEY_ROWID = "_id"; private final Context mContext; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; private static final String DB_CREATE_KEY = "create table " + DATABASE_USERKEY + " (" + "userkey text not null" +");"; private static final String DB_CREATE_DATA = "create table " + DATABASE_TABLE + " (" + "_id integer primary key autoincrement, " + "title text not null" + "data text" +");"; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DB_CREATE_KEY); db.execSQL(DB_CREATE_DATA); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS myuserkey"); db.execSQL("DROP TABLE IF EXISTS myuserdata"); onCreate(db); } } public DBAdapter(Context ctx) { this.mContext = ctx; } public DBAdapter Open() throws SQLException{ try { mDbHelper = new DatabaseHelper(mContext); } catch(Exception e){ Log.e(TAG, e.toString()); } mDb = mDbHelper.getWritableDatabase(); return this; } public void close(){ mDbHelper.close(); } public Long storeKey(String userKey){ ContentValues initialValues = new ContentValues(); initialValues.put(KEY_USERKEY, userKey); try { mDb.delete(DATABASE_USERKEY, "1=1", null); } catch(Exception e) { Log.e(TAG, e.toString()); } return mDb.insert(DATABASE_USERKEY, null, initialValues); } public String retrieveKey() { final Cursor c; try { c = mDb.query(DATABASE_USERKEY, new String[] { KEY_USERKEY}, null, null, null, null, null); }catch(Exception e){ Log.e(TAG, e.toString()); return ""; } if(c.moveToFirst()){ return c.getString(0); } else{ Log.d(TAG, "UserKey Empty"); } return ""; } //not including any function related to "myuserdata" table } Class1.java { mUserKey = mDbHelper.retrieveKey(); mDbHelper.storeKey(Key); } the error that i am receiving is from Log.e(TAG, e.toString()) in the methods retrieveKey() and storeKey() "no such table: myuserkey: , while compiling: SELECT userkey FROM myuserkey"

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  • SQL (mySQL) update some value in all records processed by a select

    - by jdmuys
    I am using mySQL from their C API, but that shouldn't be relevant. My code must process records from a table that match some criteria, and then update the said records to flag them as processed. The lines in the table are modified/inserted/deleted by another process I don't control. I am afraid in the following, the UPDATE might flag some records erroneously since the set of records matching might have changed between step 1 and step 3. SELECT * FROM myTable WHERE <CONDITION>; # step 1 <iterate over the selected set of lines. This may take some time.> # step 2 UPDATE myTable SET processed=1 WHERE <CONDITION> # step 3 What's the smart way to ensure that the UPDATE updates all the lines processed, and only them? A transaction doesn't seem to fit the bill as it doesn't provide isolation of that sort: a recently modified record not in the originally selected set might still be targeted by the UPDATE statement. For the same reason, SELECT ... FOR UPDATE doesn't seem to help, though it sounds promising :-) The only way I can see is to use a temporary table to memorize the set of rows to be processed, doing something like: CREATE TEMPORARY TABLE workOrder (jobId INT(11)); INSERT INTO workOrder SELECT myID as jobId FROM myTable WHERE <CONDITION>; SELECT * FROM myTable WHERE myID IN (SELECT * FROM workOrder); <iterate over the selected set of lines. This may take some time.> UPDATE myTable SET processed=1 WHERE myID IN (SELECT * FROM workOrder); DROP TABLE workOrder; But this seems wasteful and not very efficient. Is there anything smarter? Many thanks from a SQL newbie.

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  • Mysql results sorted by list which is unique for each user

    - by ADAM
    Ive got a table of thousands of products and 50 or so authenticated users. These users all show the products on their own web sites and they all require the ability to have them ordered differently. Im guesing i need some kind of seperate table for the orders which contains the product_id, user_id and order column? How do i do this the most efficiently in mysql so as to be very fast, and not slow down if i get millions of products in the database. Is it even wise to do it in mysql or should i be using some kind of other index like solr/lucene? My Product table is called "products" My User table is called "users" A good example of the functionality i need is google search where you can order/supress the results if you are logged in. edit: the product results will be paginated and the users have the authority to edit the products, so its not just ready only

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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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  • 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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  • Mysql - Summary Tables

    - by jwzk
    Which method do you suggest and why? Creating a summary table and . . . 1) Updating the table as the action occurs in real time. 2) Running group by queries every 15 minutes to update the summary table. 3) Something else? The data must be near real time, it can't wait an hour, a day, etc.

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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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  • When I make a database change, how do I know what needs to be removed and readded to the LinqToSql O

    - by Michael Maddox
    For example, I alter a column in a table to be not null from null. I need to then delete and readd the table. That part is pretty clear. What about views, functions, and stored procedures that access the table, especially that column in the table? I've tried running diffs against the files generated by SQLMetal with some limited success, but even with that it's fairly unclear. I know there is at least one commercial tool out there that claims to address this problem, but I am looking for something free. How are people dealing with this issue?

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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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  • MS SQL share identitiy seed amongst tables

    - by Net Citizen
    In MS SQL is it possible to share an identity seed across tables? For example I may have 2 tables: Table: PeopleA id name Table: PeopleB id name I'd like for PeopleA.id and PeopleB.id to always have unique values between themselves. I.e. I want them to share the same Identity seed. Note: I do not want to hear about table partitioning please, only about if it's possible to share a seed across tables.

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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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  • 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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