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  • Optimize MySQL database query

    - by rajeeesh
    I had a commenting application in my web site. The comments will store in a MySQL table . table structure as follows id | Comment | user | created_date ------------------------------------------------------ 12 | comment he | 1245 | 2012-03-30 12:15:00 ------------------------------------------------------ I need to run a query for listing all the comments after a specific time. ie .. a query like this SELECT * FROM comments WHERE created_date > "2012-03-29 12:15:00" ORDER BY created_date DESC Its working fine.. My question is if I got a 1-2 lakh entry in this table is this query is sufficient for the purpose ? or this query will take time to execute ? In most cases I have to show last 2 days data + periodically ( interval of 10 mins ) checking for updates with ajax from this table ... Please help Thanks

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  • nhibernate activerecord lazy collection with custom query

    - by George Polevoy
    What i'm trying to accomplish, is having a temporal soft delete table. table Project(ID int) table ProjectActual(ProjectID int, IsActual bit, ActualAt datetime) Now is it possible to map a collection of actual projects, where project is actual when there is no record in ProjectActual.ProjectID = ID, or the last record sorted by ActualAt descending has IsActual set to 1 (true)?

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  • What the heck is the "Structure and Interpretation of Computer Programs" cover drawing about?

    - by Paul Reiners
    What the heck is the Structure and Interpretation of Computer Programs cover drawing about? I mean I know what "eval", "apply", and '?' all mean, but I'm having a hard time deciphering the rest of the picture. Who the heck is the maiden? Does she work for the wizard? Why the heck is she pointing at the table? Is she pointing at that little bowl-type thing? Or the books? Or the table in general? Is she trying to tell the wizard that he should apply some sort of Lisp wizardry to the table or the items on it? Or is she just telling him something prosaic, such as his food is getting cold? What the heck is the one leg on that table that looks like...a leg...with a foot at the end (as legs tend to have)? How does the table balance on one leg? (Or is that another leg in the shadows?) [Note: I'm waiting for a lengthy build to finish in case you were wondering.]

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  • How to save to two tables using one SQLAlchemy model

    - by Oatman
    I have an SQLAlchemy ORM class, linked to MySQL, which works great at saving the data I need down to the underlying table. However, I would like to also save the identical data to a second archive table. Here's some psudocode to try and explain what I mean my_data = Data() #An ORM Class my_data.name = "foo" #This saves just to the 'data' table session.add(my_data) #This will save it to the identical 'backup_data' table my_data_archive = my_data my_data_archive.__tablename__ = 'backup_data' session.add(my_data_archive) #And commits them both session.commit() Just a heads up, I am not interested in mapping a class to a JOIN, as in: http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables

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  • Iterating over a database column in Django

    - by curious
    I would like to iterate a calculation over a column of values in a MySQL database. I wondered if Django had any built-in functionality for doing this. Previously, I have just used the following to store each column as a list of tuples with the name table_column: import MySQLdb import sys try: conn = MySQLdb.connect (host = "localhost", user = "user", passwd="passwd", db="db") except MySQLdb.Error, e: print "Error %d: %s" % (e.args[0], e.args[1]) sys.exit (1) cursor = conn.cursor() for table in ['foo', 'bar']: for column in ['foobar1', 'foobar2']: cursor.execute('select %s from %s' % (column, table)) exec "%s_%s = cursor.fetchall()" % (table, column) cursor.close() conn.commit() conn.close() Is there any functionality built into Django to more conveniently iterate through the values of a column in a database table? I'm dealing with millions of rows so speed of execution is important.

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  • Looking for nice Javascript/jQuery code for displaying large tables

    - by misha-moroshko
    I have an HTML table which may contain thousands of rows (number of columns is not a problem here). I would like to be able to browse this table easily and be able to do the following: Decide how many rows will be presented Jump to the next/previous X number of rows Scroll the table using the scroll bars to any desired line Be able to customize/extend easily this Javascript/jQuery code Has anyone seen something similar ? Thank you very much !

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  • spliiting code in java-don't know what's wrong [closed]

    - by ???? ?????
    I'm writing a code to split a file into many files with a size specified in the code, and then it will join these parts later. The problem is with the joining code, it doesn't work and I can't figure what is wrong! This is my code: import java.io.*; import java.util.*; public class StupidSplit { static final int Chunk_Size = 10; static int size =0; public static void main(String[] args) throws IOException { String file = "b.txt"; int chunks = DivideFile(file); System.out.print((new File(file)).delete()); System.out.print(JoinFile(file, chunks)); } static boolean JoinFile(String fname, int nChunks) { /* * Joins the chunks together. Chunks have been divided using DivideFile * function so the last part of filename will ".partxxxx" Checks if all * parts are together by matching number of chunks found against * "nChunks", then joins the file otherwise throws an error. */ boolean successful = false; File currentDirectory = new File(System.getProperty("user.dir")); // File[] fileList = currentDirectory.listFiles(); /* populate only the files having extension like "partxxxx" */ List<File> lst = new ArrayList<File>(); // Arrays.sort(fileList); for (File file : fileList) { if (file.isFile()) { String fnm = file.getName(); int lastDot = fnm.lastIndexOf('.'); // add to list which match the name given by "fname" and have //"partxxxx" as extension" if (fnm.substring(0, lastDot).equalsIgnoreCase(fname) && (fnm.substring(lastDot + 1)).substring(0, 4).equals("part")) { lst.add(file); } } } /* * sort the list - it will be sorted by extension only because we have * ensured that list only contains those files that have "fname" and * "part" */ File[] files = (File[]) lst.toArray(new File[0]); Arrays.sort(files); System.out.println("size ="+files.length); System.out.println("hello"); /* Ensure that number of chunks match the length of array */ if (files.length == nChunks-1) { File ofile = new File(fname); FileOutputStream fos; FileInputStream fis; byte[] fileBytes; int bytesRead = 0; try { fos = new FileOutputStream(ofile,true); for (File file : files) { fis = new FileInputStream(file); fileBytes = new byte[(int) file.length()]; bytesRead = fis.read(fileBytes, 0, (int) file.length()); assert(bytesRead == fileBytes.length); assert(bytesRead == (int) file.length()); fos.write(fileBytes); fos.flush(); fileBytes = null; fis.close(); fis = null; } fos.close(); fos = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find file"); successful = false; return successful; } catch (IOException ioe) { System.out.println("Cannot write to disk"); successful = false; return successful; } /* ensure size of file matches the size given by server */ successful = (ofile.length() == StupidSplit.size) ? true : false; } else { successful = false; } return successful; } static int DivideFile(String fname) { File ifile = new File(fname); FileInputStream fis; String newName; FileOutputStream chunk; //int fileSize = (int) ifile.length(); double fileSize = (double) ifile.length(); //int nChunks = 0, read = 0, readLength = Chunk_Size; int nChunks = 0, read = 0, readLength = Chunk_Size; byte[] byteChunk; try { fis = new FileInputStream(ifile); StupidSplit.size = (int)ifile.length(); while (fileSize > 0) { if (fileSize <= Chunk_Size) { readLength = (int) fileSize; } byteChunk = new byte[readLength]; read = fis.read(byteChunk, 0, readLength); fileSize -= read; assert(read==byteChunk.length); nChunks++; //newName = fname + ".part" + Integer.toString(nChunks - 1); newName = String.format("%s.part%09d", fname, nChunks - 1); chunk = new FileOutputStream(new File(newName)); chunk.write(byteChunk); chunk.flush(); chunk.close(); byteChunk = null; chunk = null; } fis.close(); System.out.println(nChunks); // fis = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find the given file"); System.exit(-1); } catch (IOException ioe) { System.out .println("Error while creating file chunks. Exiting program"); System.exit(-1); }System.out.println(nChunks); return nChunks; } } }

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  • MySQL - Update the same column twice

    - by uzioriluzan
    Hello, I need to update a column in a mysql table. If I do it in two steps as below, is the column "col" updated twice in the disk ? update table SET col=3*col, col=col+2; or is it written only once as in : update table SET col=3*col+2; Thanks

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  • insert exclusive locking

    - by Markus
    Hi, I have thought about the following SQL statements: INSERT INTO A(a1, a2) SELECT b1, udf_SomeFunc(b1) FROM B Where udf_SomeFunc makes a select on table A. As I understand, first, a shared lock is set on A (I am talking just about table A now), then, after this lock is released, an exclusive lock is obtained to insert the data. The question is: is it possible, that another transaction will get the exclusive lock on table A, just before the current transaction takes its exclusive lok on A?

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  • is it safe to refactor my django models?

    - by Johnd
    My model is similar to this. Is this ok or should I make the common base class abstract? What are the differcenes between this or makeing it abstract and not having an extra table? It seems odd that there is only one primary key now that I have factored stuff out. class Input(models.Model): details = models.CharField(max_length=1000) user = models.ForeignKey(User) pub_date = models.DateTimeField('date published') rating = models.IntegerField() def __unicode__(self): return self.details class Case(Input): title = models.CharField(max_length=200) views = models.IntegerField() class Argument(Input): case = models.ForeignKey(Case) side = models.BooleanField() is this ok to factor stuff out intpu Input? I noticed Cases and Arguments share a primary Key. like this: CREATE TABLE "cases_input" ( "id" integer NOT NULL PRIMARY KEY, "details" varchar(1000) NOT NULL, "user_id" integer NOT NULL REFERENCES "auth_user" ("id"), "pub_date" datetime NOT NULL, "rating" integer NOT NULL ) ; CREATE TABLE "cases_case" ( "input_ptr_id" integer NOT NULL PRIMARY KEY REFERENCES "cases_input" ("id"), "title" varchar(200) NOT NULL, "views" integer NOT NULL ) ; CREATE TABLE "cases_argument" ( "input_ptr_id" integer NOT NULL PRIMARY KEY REFERENCES "cases_input" ("id"), "case_id" integer NOT NULL REFERENCES "cases_case" ("input_ptr_id"), "side" bool NOT NULL )

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  • Creating temporary tables in MySQL Stored Procedure

    - by burntblark
    The following procedure gives me an error when I invoke it using the CALL statement: CREATE DEFINER=`user`@`localhost` PROCEDURE `emp_performance`(id VARCHAR(10)) BEGIN DROP TABLE IF EXISTS performance; CREATE TABLE performance AS SELECT time_in, time_out, day FROM attendance WHERE employee_id = id; END The error says "Unknown table 'performance' ". This is my first time actually using stored procedures and I got my sources from Google. I just cant figure out what I am doing wrong.

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  • When using SELECT can you modify the value of a returned field based on other fields?

    - by user570759
    When using MySQL SELECT can you change the value of a returned field based on other fields? For example, if I have this select: SELECT city,state,country FROM table Now if city is empty AND state is empty, I want the value of country to returned empty as well (whether country actually has a value or not). Example table: id | city | state | country ----------------------------- 1 | Here | There | MyCountry 2 | | | YourCountry So with the above table, I want the results for id=1 to return Here,There,MyCountry but the results for id=2 should be empty,empty,empty Thanks

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  • Updating an integer defined column in a MySQL DB with PHP

    - by Zloy Smiertniy
    I have a table defined like this: create table users ( id int(10), age int(3), name varchar (50) ) I want to use a query to update just age, which is an integer, that comes from an html form. When it arrives to the method that updates it, it comes as a string, so I change it to integer with PHP and try to update the table, but it doesn't work $age = intval($age); $q2 = "UPDATE users SET age='$age' where username like '$username';"; mysql_query($q2,$con);

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  • How can I treat a sequence value like a generated key?

    - by Jeff Knecht
    Here is my situation and my constraints: I am using Java 5, JDBC, and DB2 9.5 My database table contains a BIGINT value which represents the primary key. For various reasons that are too complicated to go into here, the way I insert records into the table is by executing an insert against a VIEW; an INSTEAD OF trigger retrieves the NEXT_VAL from a SEQUENCE and performs the INSERT into the target table. I can change the triggers, but I cannot change the underlying table or the general approach of inserting through the view. I want to retrieve the sequence value from JDBC as if it were a generated key. Question: How can I get access to the value pulled from the SEQUENCE. Is there some message I can fire within DB2 to float this sequence value back to the JDBC driver?

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  • Logic: Best way to sample & count bytes of a 100MB+ file

    - by Jami
    Let's say I have this 170mb file (roughly 180 million bytes). What I need to do is to create a table that lists: all 4096 byte combinations found [column 'bytes'], and the number of times each byte combination appeared in it [column 'occurrences'] Assume two things: I can save data very fast, but I can update my saved data very slow. How should I sample the file and save the needed information? Here're some suggestions that are (extremely) slow: Go through each 4096 byte combinations in the file, save each data, but search the table first for existing combinations and update it's values. this is unbelievably slow Go through each 4096 byte combinations in the file, save until 1 million rows of data in a temporary table. Go through that table and fix the entries (combine repeating byte combinations), then copy to the big table. Repeat going through another 1 million rows of data and repeat the process. this is faster by a bit, but still unbelievably slow This is kind of like taking the statistics of the file. NOTE: I know that sampling the file can generate tons of data (around 22Gb from experience), and I know that any solution posted would take a bit of time to finish. I need the most efficient saving process

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  • SQLite3 and "cascade" SELECTion

    - by SK9
    I have a parent table and a child table related to the parent table by some REFERENCE. Suppose I exec a SELECT statement on the child and that it returns the at least one result. Can I arrange for my search to automatically yield all the content of all related parents with this child too? Or must I always take the reference from the child and put this in a second SELECT statement and exec this myself?

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  • Mysql dropping inserts with triggers

    - by user2891127
    Using mysql 5.5. I have two tables. One has a whitelist of hashes. When I insert a new row into the other table, I want to first compare the hash in the insert statement to the whitelist. If it's in the whitelist, I don't want to do the insert (less data to plow through later). The inserts are generated from another program and are text files with sql statements. I've been playing with triggers, and almost have it working: BEGIN IF (select count(md5hash) from whitelist where md5hash=new.md5hash) 0 THEN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Already Whitelisted'; END IF; END But there's a problem. The Signal throwing up the error stops the import. I want to skip that line, not stop the whole import. Some searching didn't find any way to silently skip the import. My next idea was to create a duplicate table definition, and redirect the insert to that dup table. But the old and new don't seem to apply to table names. Other then adding an ignore column to my table then doing a mass drop based on that column after the import, is there any way to achieve my goal?

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  • How to create reference tables using fluent nhibernate

    - by Akk
    How can i create a 3 table schema from the following model classes. public class Product { public int Id {get; set;} public string Name {get; set;} public IList<Photo> Photos {get; set;} } public class Photo { public int Id {get; set;} public string Path {get; set;} } I want to create the following table structure in the database: Product ------- Id Name ProductPhotos ------------- ProductId (FK Products.Id) PhotoId (FK Photos.Id) Photos ------ Id Path How i can express the above Database Schema using Fluent NHibernate? I could only manage the following the Mapping but this does not get me the 3rd Photo ref table. public class ProductMap : ClassMap<Product> { public CityMap() { Id(x => x.Id); Map(x => x.Name); Table("Products"); HasMany(x => x.Photos).Table("ProductPhotos").KeyColumn("ProductId"); } }

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  • how to know on which column,the sequence is applied?

    - by Vineet
    I have to fetch all sequences with their table name along with the column name on which sequence is applied .Some how i managed to fetch table name corresponding to sequence because in my data base sequence is stored with first name as table name from data dictionary(all_sequences and all_tables) . Please let me know how to fetch corresponding column name also if possible!!

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  • C# : Problem in creating diffrent types of columns in a gridview

    - by Royson
    My windows form application has a grid view control with filename as a default column. User should create a column of following types Text, Number, Currency, Combo Box, Check Box, Radio Button ,Date time type (should display DateTimePicker control) and Hyper Link type. After that i want to pass all rows to next screen for further processing. We can create a column of these types in a grid view but how can i store it in a data table so that i can pass it to next screen. Or should i create a column in a data table and then assign data table to grid view by gridview.DataSource = dt; but can we create a these types of columns in a data table. I am so confused!! Please help me to solve this problem. Thanks

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  • I can't able to edit my column name after saving

    - by Midhun M
    I create a new table of employee now I want to edit one of the column name in that table. I can edit but while saving a pop up window asks to save some text file. How may I resolve this? Is it possible to edit without creating a new table? The text file is /* Friday, August 22, 20144:32:53 PM User: Server: MIDHUN\SQLEXPRESS Database: LinQ Application: */ employee

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  • database assignment

    - by eric
    Hi, Given the following table: CREATE TABLE T1 (A INTEGER NOT NULL); CREATE TABLE T3 (A SMALLINT NOT NULL); INSERT T1 VALUES (32768.5); SELECT * FROM T1; INSERT T3 SELECT * FROM T1; SELECT * FROM T3; What is the output of above query? If any error occured please declare the line of it?Explain your answer!

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  • Question on different ways to link tables

    - by dotnetdev
    What is the difference between linking two tables and then the PK is an FK in the other table, but the FK has not got the primary key option (so it does not have the gold key), and having the PK in one table as a PK in another table? Am I right to think that the second option is for a many-to-many relationship? Thanks

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  • Making a many-to-many relationship using DataRelations object

    - by dotnetdev
    Hi, I have about 200 tables which need to relate to another table in a many-to-many fashion. I have the tables (including the intersection table) ready IN SQL Server. How can I write code using the data relation object to make the relationship? The tables are: PartStatPartName PartsMaterialsIntersection << Materials The materials table needs to have a foreign key from the PartStatPartName table. I tried various approaches using the DataRelation class but the change did not sync to SQL Server, despite being connected and adding the relation, and then calling AcceptChanges() on the dataset. Any guidance much appreciated. I have seen some threads covering the same problem but need an example in code so I can follow the right method. Thanks

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