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• Commercial web application--scalable database design

  - by Rob Campbell

  I'm designing a set of web apps to track scientific laboratory data. Each laboratory has several members, each of whom will access both their own data and that of their laboratory as a whole. Many typical queries will thus be expected to return records of multiple members (e.g. my mouse, joe's mouse and sally's mouse). I think I have the database fairly well normalized. I'm now wondering how to ensure that users can efficiently access both their own data and their lab's data set when it is mixed among (hopefully) a whole ton of records from other labs. What I've come up with so far is that most tables will end with two fields: user_id and labgroup_id. The WHERE clause of any SELECT statement will include the appropriate reference to one of the id fields ("...WHERE 'labroup_id=n..." or "...WHERE user_id=n..."). My questions are: Is this an approach that will scale to 10^6 or more records? If so, what's the best way to use these fields in a query so that it most efficiently searches the relevant subset of the database? e.g. Should the first step in querying be to create a temporary table containing just the labgroup's data? Or will indexing using some combination of the id, user_id, and labroup_id fields be sufficient at that scale? I thank any responders very much in advance.

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• Getting the avg of the top 10 students from each school

  - by dave

  Hi all -- We have a school district with 38 elementary schools. The kids took a test. The averages for the schools are widely dispersed, but I want to compare the averages of JUST THE TOP 10 students from each school. Requirement: use temporary tables only. I have done this in a very work-intensive, error-prone sort of way as follows. (sch_code = e.g., 9043; -- schabbrev = e.g., "Carter"; -- totpct_stu = e.g., 61.3) DROP TEMPORARY TABLE IF EXISTS avg_top10 ; CREATE TEMPORARY TABLE avg_top10 ( sch_code VARCHAR(4), schabbrev VARCHAR(75), totpct_stu DECIMAL(5,1) ); INSERT INTO avg_top10 SELECT sch_code , schabbrev , totpct_stu FROM test_table WHERE sch_code IN ('5489') ORDER BY totpct_stu DESC LIMIT 10; -- I do that last query for EVERY school, so the total -- length of the code is well in excess of 300 lines. -- Then, finally... SELECT schabbrev, ROUND( AVG( totpct_stu ), 1 ) AS top10 FROM avg_top10 GROUP BY schabbrev ORDER BY top10 ; -- OUTPUT: ----------------------------------- schabbrev avg_top10 ---------- --------- Goulding 75.4 Garth 77.7 Sperhead 81.4 Oak_P 83.7 Spring 84.9 -- etc... Question: So this works, but isn't there a lot better way to do it? Thanks! PS -- Looks like homework, but this is, well...real.

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• MySQL query optimization - distinct, order by and limit

  - by Manuel Darveau

  I am trying to optimize the following query: select distinct this_.id as y0_ from Rental this_ left outer join RentalRequest rentalrequ1_ on this_.id=rentalrequ1_.rental_id left outer join RentalSegment rentalsegm2_ on rentalrequ1_.id=rentalsegm2_.rentalRequest_id where this_.DTYPE='B' and this_.id<=1848978 and this_.billingStatus=1 and rentalsegm2_.endDate between 1273631699529 and 1274927699529 order by rentalsegm2_.id asc limit 0, 100; This query is done multiple time in a row for paginated processing of records (with a different limit each time). It returns the ids I need in the processing. My problem is that this query take more than 3 seconds. I have about 2 million rows in each of the three tables. Explain gives: +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+----------------------------------------------+ | 1 | SIMPLE | rentalsegm2_ | range | index_endDate,fk_rentalRequest_id_BikeRentalSegment | index_endDate | 9 | NULL | 449904 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | rentalrequ1_ | eq_ref | PRIMARY,fk_rental_id_BikeRentalRequest | PRIMARY | 8 | solscsm_main.rentalsegm2_.rentalRequest_id | 1 | Using where | | 1 | SIMPLE | this_ | eq_ref | PRIMARY,index_billingStatus | PRIMARY | 8 | solscsm_main.rentalrequ1_.rental_id | 1 | Using where | +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+----------------------------------------------+ I tried to remove the distinct and the query ran three times faster. explain without the query gives: +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+-----------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+-----------------------------+ | 1 | SIMPLE | rentalsegm2_ | range | index_endDate,fk_rentalRequest_id_BikeRentalSegment | index_endDate | 9 | NULL | 451972 | Using where; Using filesort | | 1 | SIMPLE | rentalrequ1_ | eq_ref | PRIMARY,fk_rental_id_BikeRentalRequest | PRIMARY | 8 | solscsm_main.rentalsegm2_.rentalRequest_id | 1 | Using where | | 1 | SIMPLE | this_ | eq_ref | PRIMARY,index_billingStatus | PRIMARY | 8 | solscsm_main.rentalrequ1_.rental_id | 1 | Using where | +----+-------------+--------------+--------+-----------------------------------------------------+---------------+---------+--------------------------------------------+--------+-----------------------------+ As you can see, the Using temporary is added when using distinct. I already have an index on all fields used in the where clause. Is there anything I can do to optimize this query? Thank you very much!

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• Do you have health checks in your web app or web site?

  - by Pekka

  I have built PHP based "health check" scripts for several projects, but they were always custom-made for the occasion and not written for abstraction as an independent product. I would like to know whether such a solution exists. What I meam by "health check" is a protected web page that functions much like a suite of unit tests, but on a more operational level, showing red/yellow/green statuses for things like Are the cache directories writable? Is the PHP version correct, are required extensions installed? Is the configuration file protected from writing? Is the database server reachable? Do the key tables exist in the database? Is there enough disk space available? Is the site's front page reachable and renders fully ( = no PHP errors)? Do the project's libraries' MD5 checksums match the original ones? Do you do this - or parts of it - in your applications and web sites? Are there any standardized tools for this that bring along all the functionality to perform the tests (ideally as plugins), and just need to be configured accordingly? Is there a way to set this up using one of the Unit Testing frameworks available for PHP (preferably PHPUnit)? If so, do you know any resources / tutorials outlining how?

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• How to use Hibernate SchemaUpdate class with a JPA persistence.xml?

  - by John Rizzo

  I've a main method using SchemaUpdate to display at the console what tables to alter/create and it works fine in my Hibernate project: public static void main(String[] args) throws IOException { //first we prepare the configuration Properties hibProps = new Properties(); hibProps.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("jbbconfigs.properties")); Configuration cfg = new AnnotationConfiguration(); cfg.configure("/hibernate.cfg.xml").addProperties(hibProps); //We create the SchemaUpdate thanks to the configs SchemaUpdate schemaUpdate = new SchemaUpdate(cfg); //The update is executed in script mode only schemaUpdate.execute(true, false); ... I'd like to reuse this code in a JPA project, having no hibernate.cfg.xml file (and no .properties file), but a persistence.xml file (autodetected in the META-INF directory as specified by the JPA spec). I tried this too simple adaptation, Configuration cfg = new AnnotationConfiguration(); cfg.configure(); but it failed with that exception. Exception in thread "main" org.hibernate.HibernateException: /hibernate.cfg.xml not found Has anybody done that? Thanks.

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• Using Subsonic 3.0 Advanced Templates

  - by umit

  Hi all, I've been trying to use Subsonic Advanced Templates in a project for a while but most of the time I find myself writing a Stored Procedure as I can't find a proper way of doing it in code. Subsonic created corresponding objects for my DB tables and for foreign keys it created IQueryable fields inside each object. These fields are not loaded by default and a new SQL query is executed when you access them. 1- Is there a way to get all data in one query (deep load)? Also these fields can not be assigned. So when I want to create an object in a maintenance page, I can't put all the data into this object before saving it in DB: Post post = new Post(); //get photos for this post IList<PostPhoto> postPhotos = GetPostPhotos(); post.PostPhotos = postPhotos; 2- Is it possible to have one Post object with all fields set from user input? Think of the Post object above and assume I've successfully assigned its fields. Now I need to save it to the DB. 3- Is using BatchQuery the only way to do it in one query? If I have 4 photos in PostPhotos field; 2 of them previously saved and 2 of them new, can I use the Update method to handle both the adding and updating of these photos? Any ideas or links are appreciated. Cheers...

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• How can I make this LinqToSQL query work? (SqlExecption)

  - by kversch

  The following code gives me an SqlException: OO theCourse = subject.Course; var students = dc.studentsCourses.Where(x = x.course == theCourse).Select(x = x.student); "Invalid object name 'dbo.studentsCourses'." I tried the following code instead but I also get an Exception. My original question was asked on Aardvark and can be read bellow: var allStudents = from s in dc.students select s; List thestudents = new List(); foreach (student s in allStudents) { if (s.courses.Contains(theCourse)) { thestudents.Add(s); } } I did a right click, "run custom tool" on my dbml and checked my names of my tables and entities. The project compiles but I get an Exception at runtime on this line: "if (s.courses.Contains(theCourse))" Any ideas? Original question on Aardvark: How do I do a LinqToSQL query that gives me this: I want to select all students that attended a certain lesson. The lesson is from a certain course. So select the course the lesson is from. Now select all the students that are following that course. There is a many-to-many relationship between the students and the courses table in my DB. I already extended my LINQ entities to be able to select student.Courses and course.Students using this method: http://www.codeproject.com/KB/linq/linq-to-sql-many-to-many.aspx

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• how to rotate around each record in linq and show that in view

  - by Sadegh

  Hi, I have four tables in my database and i want to join that's and return record's and show that into searchController! My query is this: public IQueryable PerformSearch(string query) { if (!string.IsNullOrEmpty(query)) { var results = from tbl1 in context.Table1 join tbl2 in context.Table2 on tbl1.Id equals tbl2.Id join tbl3 in context.Table3 on tbl2.Id equals tbl3.Id join tbl4 in context.Table4 on tbl3.Id equals tbl4.Id where tbl1.col2.Contains(query) orderby tbl1.Count descending select new { col1 = tbl1.Col1, col1 = tbl1.Col1, col1 = tbl1.Col1, . . . }; return results.AsQueryable(); } else return null; } And this method called in SearchController as below: public class SearchController : System.Web.Mvc.Controller { public System.Web.Mvc.ActionResult Search(System.String query) { var search = new Search(); ViewData["result"] = search.PerformSearch(query); return View("Search"); } } I don't know how i can rotate around each record (plus vs intellisense feature) returned by PeformSeach method and show that in view! Also is this a good way? thanks in advance

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• how to model a follower stream in appengine?

  - by molicule

  I am trying to design tables to buildout a follower relationship. Say I have a stream of 140char records that have user, hashtag and other text. Users follow other users, and can also follow hashtags. I am outlining the way I've designed this below, but there are two limitaions in my design. I was wondering if others had smarter ways to accomplish the same goal. The issues with this are The list of followers is copied in for each record If a new follower is added or one removed, 'all' the records have to be updated. The code class HashtagFollowers(db.Model): """ This table contains the followers for each hashtag """ hashtag = db.StringProperty() followers = db.StringListProperty() class UserFollowers(db.Model): """ This table contains the followers for each user """ username = db.StringProperty() followers = db.StringListProperty() class stream(db.Model): """ This table contains the data stream """ username = db.StringProperty() hashtag = db.StringProperty() text = db.TextProperty() def save(self): """ On each save all the followers for each hashtag and user are added into a another table with this record as the parent """ super(stream, self).save() hfs = HashtagFollowers.all().filter("hashtag =", self.hashtag).fetch(10) for hf in hfs: sh = streamHashtags(parent=self, followers=hf.followers) sh.save() ufs = UserFollowers.all().filter("username =", self.username).fetch(10) for uf in ufs: uh = streamUsers(parent=self, followers=uf.followers) uh.save() class streamHashtags(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() class streamUsers(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() Now, to get the stream of followed hastags indexes = db.GqlQuery("""SELECT __key__ from streamHashtags where followers = 'myusername'""") keys = [k,parent() for k in indexes[offset:numresults]] return db.get(keys) Is there a smarter way to do this?

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• MS Access (Jet) transactions, workspaces & scope

  - by Eric G

  I am having trouble with committing a transaction (using Access 2003 DAO). It's acting as if I never had called BeginTrans -- I get error 3034 on CommitTrans, "You tried to commit or rollback a transaction without first beginning a transaction"; and the changes are written to the database (presumably because they were never wrapped in a transaction). However, BeginTrans is run, if you step through it. I am running it within the Access environment using the DBEngine(0) workspace. The tables I'm updating are all opened via a Jet database connection (to the same database) and updated using DAO.Recordset.update. The connection is opened before starting BeforeTrans. I'm not doing anything weird in the middle of the transaction like closing/opening connections or multiple workspaces etc. There is one nested transaction level (basically it's wrapping multiple transacted updates in an outer transaction, so if any fail they all fail). The inner transactions run without errors, it's the outer transaction that doesn't work. Here are a few things I've looked into and ruled out: The transaction is spread across several methods and BeginTrans and CommitTrans (and Rollback) are all in different places. But when I tried a simple test of running a transaction this way, it doesn't seem like this should matter. I thought maybe the database connection gets closed when it goes out of local scope, even though I have another 'global' reference to it (I'm never sure what DAO does with dbase connections to be honest). But this seems not to be the case -- right before the commit, the connection and its recordsets are alive (I can check their properties, EOF = False, etc.) My CommitTrans and Rollback are done within event callbacks. (Very basically, a parser program is throwing an 'onLoad' or 'onLoadFail' event at the end of parsing, which I am handling by either committing or rolling back the inserts I made during processing.) However, again, trying a simple test, it doesn't seem like this should matter. Any ideas why this isn't working for me? Thanks.

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• multi-shop orders table and sequential order numbers based on shop

  - by imanc

  Hey, I am looking at building a shop solution that needs to be scalable. Currently it retrieves 1-2000 orders on average per day across multiple country based shops (e.g. uk, us, de, dk, es etc.) but this order could be 10x this amount in two years. I am looking at either using separate country-shop databases to store the orders tables, or looking to combine all into one order table. If all orders exist in one table with a global ID (auto num) and country ID (e.g uk,de,dk etc.), each countries orders would also need to have sequential ordering. So in essence, we'd have to have a global ID and a country order ID, with the country order ID being sequential for countries only, e.g. global ID = 1000, country = UK, country order ID = 1000 global ID = 1001, country = DE, country order ID = 1000 global ID = 1002, country = DE, country order ID = 1001 global ID = 1003, country = DE, country order ID = 1002 global ID = 1004, country = UK, country order ID = 1001 THe global ID would be DB generated and not something I would need to worry about. But I am thinking that I'd have to do a query to get the current country order based ID+1 to find the next sequential number. Two things concern me about this: 1) query times when the table has potentially millions of rows of data and I'm doing a read before a write, 2) the potential for ID number clashes due to simultaneous writes/reads. With a MyISAM table the entire table could be locked whilst the last country order + 1 is retrieved, to prevent ID number clashes. I am wondering if anyone knows of a more elegant solution? Cheers, imanc

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• JPA concatenating table names for parent/child @OneToMany

  - by Robert

  We are trying to use a basic @OneToMany relationship: @Entity @Table(name = "PARENT_MESSAGE") public class ParentMessage { @Id @Column(name = "PARENT_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer parentId; @OneToMany(fetch=FetchType.LAZY) private List childMessages; public List getChildMessages() { return this.childMessages; } ... } @Entity @Table(name = "CHILD_MSG_USER_MAP") public class ChildMessage { @Id @Column(name = "CHILD_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer childId; @ManyToOne(optional=false,targetEntity=ParentMessage.class,cascade={CascadeType.REFRESH}, fetch=FetchType.LAZY) private ParentMessage parentMsg; public ParentMessage getParentMsg() { return parentMsg; } ... } ChildMessage child = new ChildMessage(); em.getTransaction().begin(); ParentMessage parentMessage = (ParentMessage) em.find(ParentMessage.class, parentId); child.setParentMsg(parentMessage); List list = parentMessage.getChildMessages(); if(list == null) list = new ArrayList(); list.add(child); em.getTransaction().commit(); We receive the following error. Why is OpenJPA concatenating the table names to APP.PARENT_MESSAGE_CHILD_MSG_USER_MAP? Of course that table doesn't exist.. the tables defined are APP.PARENT_MESSAGE and APP.CHILD_MSG_USER_MAP Caused by: org.apache.openjpa.lib.jdbc.ReportingSQLException: Table/View 'APP.PARENT_MESSAGE_CHILD_MSG_USER_MAP' does not exist. {SELECT t1.CHILD_ID, t1.PARENT_ID, t1.CREATED_TIME, t1.USER_ID FROM APP.PARENT_MESSAGE_CHILD_MSG_USER_MAP t0 INNER JOIN APP.CHILD_MSG_USER_MAP t1 ON t0.CHILDMESSAGES_CHILD_ID = t1.CHILD_ID WHERE t0.PARENTMESSAGE_PARENT_ID = ?} [code=30000, state=42X05]

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• Selenium RC: Selecting elements using the CSS :contains pseudo-class

  - by Andrew

  I would like to assert that a table row contains the data that I expect in two different tables. Using the following HTML as an example: <table> <tr> <th>Table 1</th> </tr> <tr> <td>Row 1 Col 1</td> <td>Row 1 Col 2</td> </tr> </table> <table> <tr> <th>Table 2</th> </tr> <tr> <td>Row 1 Col 1</td> <td>different data</td> </tr> </table> The following assertion passes: $this->assertElementPresent('css=table:contains(Table 1)'); However, this one doesn't: $this->assertElementPresent('css=table:contains(Table 1) tr:contains(Row 1 Col 1)'); And ultimately, I need to be able to test that both columns within the table row contain the data that I expect: $this->assertElementPresent('css=table:contains(Table 1) tr:contains(Row 1 Col 1):contains(Row 1 Col 2)'); $this->assertElementPresent('css=table:contains(Table 2) tr:contains(Row 1 Col 1):contains(different data)'); What am I doing wrong? How can I achieve this? Update: Sounds like the problem is a bug in Selenium when trying to select descendants. The only way I was able to get this to work was to add an extra identifier on the table so I could tell which one I was working with: /* HTML */ <table id="table-1"> /* PHP */ $this->assertElementPresent("css=#table-1 tr:contains(Row 1 Col 1):contains(Row 1 Col 2)");

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• Two radically different queries against 4 mil records execute in the same time - one uses brute force.

  - by IanC

  I'm using SQL Server 2008. I have a table with over 3 million records, which is related to another table with a million records. I have spent a few days experimenting with different ways of querying these tables. I have it down to two radically different queries, both of which take 6s to execute on my laptop. The first query uses a brute force method of evaluating possibly likely matches, and removes incorrect matches via aggregate summation calculations. The second gets all possibly likely matches, then removes incorrect matches via an EXCEPT query that uses two dedicated indexes to find the low and high mismatches. Logically, one would expect the brute force to be slow and the indexes one to be fast. Not so. And I have experimented heavily with indexes until I got the best speed. Further, the brute force query doesn't require as many indexes, which means that technically it would yield better overall system performance. Below are the two execution plans. If you can't see them, please let me know and I'll re-post then in landscape orientation / mail them to you. Brute-force query: Index-based exception query: My question is, based on the execution plans, which one look more efficient? I realize that thing may change as my data grows.

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• MySQL db Audit Trail Trigger

  - by Natkeeran

  I need to track changes (audit trail) in certain tables in a MySql Db. I am trying to implement the solution suggested here. I have an AuditLog Table with the following columns: AuditLogID, TableName, RowPK, FieldName, OldValue, NewValue, TimeStamp. The mysql stored procedure is the following (this executes fine, and creates the procedure): The call to the procedure such as: CALL addLogTrigger('ProductTypes', 'ProductTypeID'); executes, but does not create any triggers (see the image). SHOW TRIGGERS returns empty set. Please let me know what could be the issue, or an alternate way to implement this. DROP PROCEDURE IF EXISTS addLogTrigger; DELIMITER $ CREATE PROCEDURE addLogTrigger(IN tableName VARCHAR(255), IN pkField VARCHAR(255)) BEGIN SELECT CONCAT( 'DELIMITER $\n', 'CREATE TRIGGER ', tableName, '_AU AFTER UPDATE ON ', tableName, ' FOR EACH ROW BEGIN ', GROUP_CONCAT( CONCAT( 'IF NOT( OLD.', column_name, ' <=> NEW.', column_name, ') THEN INSERT INTO AuditLog (', 'TableName, ', 'RowPK, ', 'FieldName, ', 'OldValue, ', 'NewValue' ') VALUES ( ''', table_name, ''', NEW.', pkField, ', ''', column_name, ''', OLD.', column_name, ', NEW.', column_name, '); END IF;' ) SEPARATOR ' ' ), ' END;$' ) FROM information_schema.columns WHERE table_schema = database() AND table_name = tableName; END$ DELIMITER ;

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• Could DataGridView be this dumb? or its me?lol

  - by Selase

  Am trying to bind data to a dropdown list on pageload based on a condition. Code explains further below. public partial class AddExhibit : System.Web.UI.Page { string adminID, caseIDRetrieved; DataSet caseDataSet = new DataSet(); SqlDataAdapter caseSqlDataAdapter = new SqlDataAdapter(); string strConn = WebConfigurationManager.ConnectionStrings["CMSSQL3ConnectionString1"].ConnectionString; protected void Page_Load(object sender, EventArgs e) { adminID = Request.QueryString["adminID"]; caseIDRetrieved = Request.QueryString["caseID"]; if (caseIDRetrieved != null) { CaseIDDropDownList.Text = caseIDRetrieved; //CaseIDDropDownList.Enabled = false; } else { try { CreateDataSet(); DataView caseDataView = new DataView(caseDataSet.Tables[0]); CaseIDDropDownList.DataSource = caseDataView; CaseIDDropDownList.DataBind(); } catch (Exception ex) { string script = "<script>alert('" + ex.Message + "');</script>"; } } } The CreateDataset method that is called in the if..else statement is contains the following code. private void CreateDataSet() { SqlConnection caseConnection = new SqlConnection(strConn); caseSqlDataAdapter.SelectCommand = new SqlCommand("Select CaseID FROM Cases", caseConnection); caseSqlDataAdapter.Fill(caseDataSet); } However when i load the page and as usual the condition that is supposed to bid the data is met, the gridview decides to displays as follows... IS IT ME OR ITS THE DATAGRID?...??

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• Oracle - UPSERT with update not executed for unmodified values

  - by Buthrakaur

  I'm using following update or insert Oracle statement at the moment: BEGIN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM; IF (SQL%ROWCOUNT = 0) THEN INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END; This runs fine except that the update statement performs dummy update if the data is same as the parameter values provided. I would not mind the dummy update in normal situation, but there's a replication/synchronization system build over this table using triggers on tables to capture updated records and executing this statement frequently for many records simply means that I'd cause huge traffic in triggers and the sync system. Is there any simple method how to reformulate this code that the update statement wouldn't update record if not necessary without using following IF-EXISTS check code which I find not sleek enough and maybe also not most efficient for this task? DECLARE CNT NUMBER; BEGIN SELECT COUNT(1) INTO CNT FROM DSMS WHERE DSM = :DSM; IF SQL%FOUND THEN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM AND (SURNAME != :SURNAME OR FIRSTNAME != :FIRSTNAME OR VALID != :VALID); ELSE INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END;

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• Ways to update a dependent table in the same MySQL transaction?

  - by codie

  I need to update two tables inside a single transaction. The individual queries look something like this: 1. INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; If the above query causes an insert then I need to run the following statement on the second table: 2. INSERT INTO t2 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = col2 + val2; otherwise, 3. UPDATE t2 SET col2 = col2 - old_val2 + val2 WHERE col1 = val1; -- old_val2 is the value of t1.col2 before it was updated Right now I run a SELECT on t1 first, to determine whether statement 1 will cause an insert or update on t1. Then I run statement 1 and either of 2 and 3 inside a transaction. What are the ways in which I can do all of these inside one transaction itself? The approach I was thinking of is the following: UPDATE t2, t1 set t2.col2 = t2.col2 - t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; INSERT INTO t2, t1 (t2.col1, t2.col2) VALUES (t1.col1, t1.col2) ON DUPLICATE KEY UPDATE t2.col2 = t2.col2 + t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; Unfortunately, there's no multi-table INSERT... ON DUPLICATE KEY UPDATE in MySQL 5.0. What else could I do?

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• Database table relationships: Always also relate to specified value (Linq to SQL in .NET Framework)

  - by sinni800

  I really can not describe my question better in the title. If anyone has suggestions: Please tell! I use the Linq to SQL framework in .NET. I ran into something which could be easily solved if the framework supported this, it would be a lot of extra coding otherwise: I have a n to n relation with a helper table in between. Those tables are: Items, places and the connection table which relates items to places and the other way. One item can be found in many places, so can one place have many items. Now of course there will be many items which will be in ALL places. Now there is a problem: Places can always be added. So I need a place-ID which encompasses ALL places, always. Like maybe a place-id "0". If the helper table has a row with the place-id of zero, this should be visible in all places. In SQL this would be a simple "Where [...] or place-id = 0", but how do I do this in Linq relations? Also, for a little side question: How could I manage "all but this place" kind of exclusions?

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• Are programming languages and methods inefficient? (assembler and C knowledge needed)

  - by b-gen-jack-o-neill

  Hi, for a long time, I am thinking and studying output of C language compiler in assembler form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually truly believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1: Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when address you desire is further translated before reaching actual RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Because you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect addressing, "my" way would be even faster. 2: Variable allocation duplicity: When you run application, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actual instruction for do so, and that actual number in memory. So, there are 2 entries of the same value in RAM. One in form of instruction, second in form of actual bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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• Yii CGridView and dropdown filter

  - by Dmitriy Gunchenko

  I created dropdown filter, it's display, but don't worked right. As I anderstand trouble in search() method view: $this->widget('zii.widgets.grid.CGridView', array( 'dataProvider'=>$model->search(), 'filter' => $model, 'columns'=>array( array( 'name' => 'client_id', 'filter' => CHtml::listData(Client::model()->findAll(), 'client_id', 'name'), 'value'=>'$data->client->name' ), 'task' ) )); I have to tables, and they relations are shown down model: public function relations() { // NOTE: you may need to adjust the relation name and the related // class name for the relations automatically generated below. return array( 'client' => array(self::BELONGS_TO, 'Client', 'client_id'), ); } public function search() { // Warning: Please modify the following code to remove attributes that // should not be searched. $criteria=new CDbCriteria; $criteria->with = array('client'); $criteria->compare('task_id',$this->task_id); $criteria->compare('client_id',$this->client_id); $criteria->compare('name',$this->client->name); $criteria->compare('task',$this->task,true); $criteria->compare('start_date',$this->start_date,true); $criteria->compare('end_date',$this->end_date,true); $criteria->compare('complete',$this->complete); return new CActiveDataProvider($this, array( 'criteria'=>$criteria, )); }

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• How would I go about sharing variables in a C++ class with Lua?

  - by Nicholas Flynt

  I'm fairly new to Lua, I've been working on trying to implement Lua scripting for logic in a Game Engine I'm putting together. I've had no trouble so far getting Lua up and running through the engine, and I'm able to call Lua functions from C and C functions from Lua. The way the engine works now, each Object class contains a set of variables that the engine can quickly iterate over to draw or process for physics. While game objects all need to access and manipulate these variables in order for the Game Engine itself to see any changes, they are free to create their own variables, a Lua is exceedingly flexible about this so I don't forsee any issues. Anyway, currently the Game Engine side of things are sitting in C land, and I really want them to stay there for performance reasons. So in an ideal world, when spawning a new game object, I'd need to be able to give Lua read/write access to this standard set of variables as part of the Lua object's base class, which its game logic could then proceed to run wild with. So far, I'm keeping two separate tables of objects in place-- Lua spawns a new game object which adds itself to a numerically indexed global table of objects, and then proceeds to call a C++ function, which creates a new GameObject class and registers the Lua index (an int) with the class. So far so good, C++ functions can now see the Lua object and easily perform operations or call functions in Lua land using dostring. What I need to do now is take the C++ variables, part of the GameObject class, and expose them to Lua, and this is where google is failing me. I've encountered a very nice method here which details the process using tags, but I've read that this method is deprecated in favor of metatables. What is the ideal way to accomplish this? Is it worth the hassle of learning how to pass class definitions around using libBind or some equivalent method, or is there a simple way I can just register each variable (once, at spawn time) with the global lua object? What's the "current" best way to do this, as of Lua 5.1.4?

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• SQL Duplicates Issue SQL SERVER 2000

  - by jeff

  I have two tables : Product and ProductRateDetail. The parent table is Product. I have duplicate records in the product table which need to be unique. There are entries in the ProductRateDetail table which correspond to duplicate records in the product table. Somehow I need to update the ProductRateDetail table to match the original (older) ID from the Product table and then remove the duplicates from the product table. I would do this manually but there are 100's of records. i.e. something like UPDATE tbl_productRateDetail SET productID = (originalID from tbl_product) then something like DELETE from tbl_product WHERE duplicate ID and only delete the recently added ID data example: (sorry can't work out this formatting thing) tbl_Product select * from dbo.Product where ProductCode = '10003' ProductID ProductTypeID ProductDescription ProductCode ProductSize 365 1 BEND DOUBLE FLANGED 10003 80mmX90deg 1354 1 BEND DOUBLE FLANGED 10003 80mmX90deg tbl_ProductRateDetail SELECT * FROM [MSTS2].[dbo].[ProductRateDetail] WHERE ProductID in (365,1354) ProductRateDetailID ProductRateID ProductID UnitRate 365 1 365 16.87 1032 5 365 16.87 2187 10 365 16.87 2689 11 365 16.87 3191 12 365 16.87 7354 21 1354 21.30 7917 22 1354 21.30 8480 23 1354 21.30 9328 25 1354 21.30 9890 26 1354 21.30 10452 27 1354 21.30 Please help!

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• Getting the most recent post based on date

  - by camcim

  Hi guys, How do I go about displaying the most recent post when I have two tables, both containing a column called creation_date This would be simple if all I had to do was get the most recent post based on posts created_on value however if a post contains replies I need to factor this into the equation. If a post has a more recent reply I want to get the replies created_on value but also get the posts post_id and subject. The posts table structure: CREATE TABLE `posts` ( `post_id` bigint(20) unsigned NOT NULL auto_increment, `cat_id` bigint(20) NOT NULL, `user_id` bigint(20) NOT NULL, `subject` tinytext NOT NULL, `comments` text NOT NULL, `created_on` datetime NOT NULL, `status` varchar(10) NOT NULL default 'INACTIVE', `private_post` varchar(10) NOT NULL default 'PUBLIC', `db_location` varchar(10) NOT NULL, PRIMARY KEY (`post_id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ; The replies table structure: CREATE TABLE `replies` ( `reply_id` bigint(20) unsigned NOT NULL auto_increment, `post_id` bigint(20) NOT NULL, `user_id` bigint(20) NOT NULL, `comments` text NOT NULL, `created_on` datetime NOT NULL, `notify` varchar(5) NOT NULL default 'YES', `status` varchar(10) NOT NULL default 'INACTIVE', `db_location` varchar(10) NOT NULL, PRIMARY KEY (`reply_id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ; Here is my query so far. I've removed my attempt of extracting the dates. $strQuery = "SELECT posts.post_id, posts.created_on, replies.created_on, posts.subject "; $strQuery = $strQuery."FROM posts ,replies "; $strQuery = $strQuery."WHERE posts.post_id = replies.post_id "; $strQuery = $strQuery."AND posts.cat_id = '".$row->cat_id."'";

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• Wnat is the preferred method of building extremely lightweight business object / DAL now that I have

  - by Seth Spearman

  Hello, I have completed a simple database for a project. Only 6tables. Of the 6, one is a "lookup" table. There is one "master" table that is the driver for the system. It is referenced as a foreign key by the other four tables. Give that this step is completed. What is the FASTEST, EASIEST way to create POCOs/BizObjects that can load load the data and the child data. Here are my CAVEATS. *I don't want to spend more than 30-60 minutes learning how? *There is very little biz logic needed in the POCOs. They will pretty much load data. Don't even really need to write back data. *I already know CSLA (up to version 3) but I feel that is overkill for this little project. *Nevertheless, I would love it if it ROOT objects could have collection classes that contain the CHILD objects as in CSLA...but again, without using CSLA. *Please give the answer for .NET 35 but also if I was restricted to only use .NET 20. *Ideally I could just point a tool at the database and the POCOs would be genn'ed. *FREE Just curious what you guys use for this kind of scenario. I understand that this question is subjective but I want to hear a variety of answers. Seth

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