database queries - Page 33

What is the right way to do flexible columns in database?

- by Timmy

Im storing columns in database with users able to add and remove columns, with fake columns. How do I implement this efficiently?

methods of joining 2 tables without using JOIN or SELECT more than one distinct table in the query

- by GB_J

Is there a way of joining results from 2 tables without using JOIN or SELECT from more than one table? The reason being the database im working with requires queries that only contain SELECT, FROM, and WHERE clauses containing only one distinct table. I do, however, need information from other tables for the project i'm working on. More info: the querier returns the query results in a .csv format, is there something we can manipulate there?

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SQL SERVER – Attach mdf file without ldf file in Database

- by pinaldave

Background Story: One of my friends recently called up and asked me if I had spare time to look at his database and give him a performance tuning advice. Because I had some free time to help him out, I said yes. I asked him to send me the details of his database structure and sample data. He said that since his database is in a very early stage and is small as of the moment, so he told me that he would like me to have a complete database. My response to him was “Sure! In that case, take a backup of the database and send it to me. I will restore it into my computer and play with it.” He did send me his database; however, his method made me write this quick note here. Instead of taking a full backup of the database and sending it to me, he sent me only the .mdf (primary database file). In fact, I asked for a complete backup (I wanted to review file groups, files, as well as few other details). Upon calling my friend, I found that he was not available. Now, he left me with only a .mdf file. As I had some extra time, I decided to checkout his database structure and get back to him regarding the full backup, whenever I can get in touch with him again. Technical Talk: If the database is shutdown gracefully and there was no abrupt shutdown (power outrages, pulling plugs to machines, machine crashes or any other reasons), it is possible (there’s no guarantee) to attach .mdf file only to the server. Please note that there can be many more reasons for a database that is not getting attached or restored. In my case, the database had a clean shutdown and there were no complex issues. I was able to recreate a transaction log file and attached the received .mdf file. There are multiple ways of doing this. I am listing all of them here. Before using any of them, please consult the Domain Expert in your company or industry. Also, never attempt this on live/production server without the presence of a Disaster Recovery expert. USE [master] GO -- Method 1: I use this method EXEC sp_attach_single_file_db @dbname='TestDb', @physname=N'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\TestDb.mdf' GO -- Method 2: CREATE DATABASE TestDb ON (FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\TestDb.mdf') FOR ATTACH_REBUILD_LOG GO Method 2: If one or more log files are missing, they are recreated again. There is one more method which I am demonstrating here but I have not used myself before. According to Book Online, it will work only if there is one log file that is missing. If there are more than one log files involved, all of them are required to undergo the same procedure. -- Method 3: CREATE DATABASE TestDb ON ( FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\TestDb.mdf') FOR ATTACH GO Please read the Book Online in depth and consult DR experts before working on the production server. In my case, the above syntax just worked fine as the database was clean when it was detached. Feel free to write your opinions and experiences for it will help the IT community to learn more from your suggestions and skills. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Backup and Restore, SQL Data Storage, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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Database Rebuild

- by Robert May

I promised I’d have a simpler mechanism for rebuilding the database. Below is a complete MSBuild targets file for rebuilding the database from scratch. I don’t know if I’ve explained the rational for this. The reason why you’d WANT to do this is so that each developer has a clean version of the database on their local machine. This also includes the continuous integration environment. Basically, you can do whatever you want to the database without fear, and in a minute or two, have a completely rebuilt database structure. DBDeploy (including the KTSC build task for dbdeploy) is used in this script to do change tracking on the database itself. The MSBuild ExtensionPack is used in this target file. You can get an MSBuild DBDeploy task here. There are two database scripts that you’ll see below. First is the task for creating an admin (dbo) user in the system. This script looks like the following: USE [master] GO If not Exists (select Name from sys.sql_logins where name = '$(User)') BEGIN CREATE LOGIN [$(User)] WITH PASSWORD=N'$(Password)', DEFAULT_DATABASE=[$(DatabaseName)], CHECK_EXPIRATION=OFF, CHECK_POLICY=OFF END GO EXEC master..sp_addsrvrolemember @loginame = N'$(User)', @rolename = N'sysadmin' GO USE [$(DatabaseName)] GO CREATE USER [$(User)] FOR LOGIN [$(User)] GO ALTER USER [$(User)] WITH DEFAULT_SCHEMA=[dbo] GO EXEC sp_addrolemember N'db_owner', N'$(User)' GO The second creates the changelog table. This script can also be found in the dbdeploy.net install\scripts directory. CREATE TABLE changelog ( change_number INTEGER NOT NULL, delta_set VARCHAR(10) NOT NULL, start_dt DATETIME NOT NULL, complete_dt DATETIME NULL, applied_by VARCHAR(100) NOT NULL, description VARCHAR(500) NOT NULL ) GO ALTER TABLE changelog ADD CONSTRAINT Pkchangelog PRIMARY KEY (change_number, delta_set) GO Finally, Here’s the targets file. <Projectxmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="4.0" DefaultTargets="Update"> <PropertyGroup> <DatabaseName>TestDatabase</DatabaseName> <Server>localhost</Server> <ScriptDirectory>.\Scripts</ScriptDirectory> <RebuildDirectory>.\Rebuild</RebuildDirectory> <TestDataDirectory>.\TestData</TestDataDirectory> <DbDeploy>.\DBDeploy</DbDeploy> <User>TestUser</User> <Password>TestPassword</Password> <BCP>bcp</BCP> <BCPOptions>-S$(Server) -U$(User) -P$(Password) -N -E -k</BCPOptions> <OutputFileName>dbDeploy-output.sql</OutputFileName> <UndoFileName>dbDeploy-output-undo.sql</UndoFileName> <LastChangeToApply>99999</LastChangeToApply> </PropertyGroup> <ImportProject="$(MSBuildExtensionsPath)\ExtensionPack\4.0\MSBuild.ExtensionPack.tasks"/> <UsingTask TaskName="Ktsc.Build.DBDeploy" AssemblyFile="$(DbDeploy)\Ktsc.Build.dll"/> <ItemGroup> <VariableInclude="DatabaseName"> <Value>$(DatabaseName)</Value> </Variable> <VariableInclude="Server"> <Value>$(Server)</Value> </Variable> <VariableInclude="User"> <Value>$(User)</Value> </Variable> <VariableInclude="Password"> <Value>$(Password)</Value> </Variable> </ItemGroup> <TargetName="Rebuild">  <MSBuild.ExtensionPack.SqlServer.SqlCmd Variables="@(Variable)" Database="$(DatabaseName)" TaskAction="Execute" CommandLineQuery ="ALTER DATABASE $(DatabaseName) SET OFFLINE WITH ROLLBACK IMMEDIATE"/>  <MSBuild.ExtensionPack.Sql2008.DatabaseTaskAction="SetOnline" DatabaseItem="$(DatabaseName)"/>  <MSBuild.ExtensionPack.Sql2008.DatabaseTaskAction="Delete" DatabaseItem="$(DatabaseName)"/>  <MSBuild.ExtensionPack.Sql2008.DatabaseTaskAction="Create" DatabaseItem="$(DatabaseName)" Force="True"/>  <MSBuild.ExtensionPack.SqlServer.SqlCmd TaskAction="Execute" Server="(local)" Database="$(DatabaseName)" InputFiles="$(RebuildDirectory)\0002 Create Admin User.sql" Variables="@(Variable)" />  <MSBuild.ExtensionPack.SqlServer.SqlCmd TaskAction="Execute" Server="(local)" Database="$(DatabaseName)" LogOn="$(User)" Password="$(Password)" InputFiles="$(RebuildDirectory)\0003 Create Changelog.sql" Variables="@(Variable)" /> <CallTarget Targets="Update;ImportData"/> </Target> <TargetName="Update" DependsOnTargets="CreateUpdateScript"> <MSBuild.ExtensionPack.SqlServer.SqlCmd TaskAction="Execute" Server="(local)" Database="$(DatabaseName)" LogOn="$(User)" Password="$(Password)" InputFiles="$(OutputFileName)" Variables="@(Variable)" /> </Target> <TargetName="CreateUpdateScript"> <ktsc.Build.DBDeploy DbType="mssql" DbConnection="User=$(User);Password=$(Password);Data Source=$(Server);Initial Catalog=$(DatabaseName);" Dir="$(ScriptDirectory)" OutputFile="..\$(OutputFileName)" UndoOutputFile="..\$(UndoFileName)" LastChangeToApply="$(LastChangeToApply)"/> </Target> <TargetName="ImportData"> <ItemGroup> <TestData Include="$(TestDataDirectory)\*.dat"/> </ItemGroup> <ExecCommand="$(BCP) $(DatabaseName).dbo.%(TestData.Filename) in"%(TestData.Identity)"$(BCPOptions)"/> </Target> </Project> Technorati Tags: MSBuild

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Crystal Reports Server - Database Login Needs to go Away

- by Trey Sargent

The environment I'm working in is a Crystal Reports Server 2008 talking to a MySQL Server 5.1 database using JDBC. The problem is that I get a database logon screen every time I try to access a report from Crystal Reports Server. I've setup a JDBC connection using the MySQL Connector/J driver. When I create a .rpt file I provide the login credentails all is fine. I then publish to InfoView and go to access the report and it prompts me for username and password to the database. I then went to CMC and right-clicked on the report and opened the Database Configuration. I've selected 'Use original database logon information from the report' and 'Use same database logon as when report is run'. However, I still get the logon screen when I try to access the report.

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Finding first alphabetic character in a DB2 database field

- by Paul Alan Taylor

I'm doing a bit of work which requires me to truncate DB2 character-based fields. Essentially, I need to discard all text which is found at or after the first alphabetic character. e.g. 102048994BLAHBLAHBLAH becomes:- 102048994 In SQL Server, this would be a doddle - PATINDEX would swoop in and save the day. Much celebration would ensue. My problem is that I need to do this in DB2. Worse, the result needs to be used in a join query, also in DB2. I can't find an easy way to do this. Is there a PATINDEX equivalent in DB2? Is there another way to solve this problem? If need be, I'll hardcode 26 chained LOCATE functions to get my result, but if there is a better way, I am all ears.

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The Boss Answer: What is a relational database?

- by kce

I'm mostly a system administrator and I don't directly work with databases other than installing them, setting up accounts, granting privileges, and so on. I realized that if The Boss walked up to me and asked, "What is a relational database?" I probably couldn't give a satisfactory answer... I'd maybe mumble something about data being stored and organized by categories which you can query with a special programing language (i.e., SQL). So could someone give a good "Boss Answer" for what a relational database is? And maybe how its different than just storing data on a file server? Bonus points for clever but accessible analogies and explaining tables, columns, records and fields. I'd define a "Boss Answer" as a quick one (maybe two) paragraph explanation for non-technical folks... mostly your Boss, on those rare occasions they actually ask you what it is you do all day.

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Using a database class in my user class

- by Josh

In my project I have a database class that I use to handle all the MySQL stuff. It connects to a database, runs queries, catches errors and closes the connection. Now I need to create a members area on my site, and I was going to build a users class that would handle registration, logging in, password/username changes/resets and logging out. In this users class I need to use MySQL for obvious reasons... which is what my database class was made for. But I'm confused as to how I would use my database class in my users class. Would I want to create a new database object for my user class and then have it close whenever a method in that class is finished? Or do I somehow make a 'global' database class that can be used throughout my entire script (if this is the case I need help with that, no idea what to do there.) Thanks for any feedback you can give me.

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upgrading to worpdress 3.5 erased all posts and pages, wiped database

- by James

So I have upgraded to wordpress 3.5 and that seemed to have erased all posts and custom post types, media images, sliders etc' I have made a backup using both pressbackup and backupbuddy but when I try to restore the database (or everything). when it is done, if I look at the front end, everything is back and looks great but then when I go to the back end it says the database needs to be upgraded and doesn't let me bypass that. if i click ok it prompts the following message and after that everything is wiped again: WordPress database error: [Table 'db446353270.wp_categories' doesn't exist] SELECT * FROM wp_categories ORDER BY cat_ID WordPress database error: [Table 'db446353270.wp_post2cat' doesn't exist] SELECT post_id, category_id FROM wp_post2cat GROUP BY post_id, category_id WordPress database error: [Table 'db446353270.wp_linkcategories' doesn't exist] SELECT cat_id, cat_name FROM wp_linkcategories WordPress database error: [Unknown column 'link_category' in 'field list'] SELECT link_id, link_category FROM wp_links please advise. Thanks

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Ecommerce Database DNS Switch

- by KThompson

Hello, I am moving an e-commerce site to a new server. All has been successful and its time to change the DNS for the domain. It's a relatively popular site and I fear that during propagation orders will be split between the old database and the new one. The databases do contain content that is dependent of the server it is on (Cache path, upload directory, etc.) so I can't just point the old site to the new database. Are there any solutions to this without any of the sites going down. Thanks in advance

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Set up Glassfish connection pool to talk to a database on a Ubuntu VPS

- by Harry Pham

On my Ubuntu VPS, i have a mysql server running and a Glassfish 3.0.1 Application Server running. And I am having a hard to have my GF successfully ping the database. Here is my GF set up Assume: x.y.z.t is the ip of my VPS Resource Type: javax.sql.ConnectionPoolDataSource User: root DatabaseName: scholar Url: jdbc:mysql://x.y.z.t:3306/scholar URL: jdbc:mysql://x.y.z.t:3306/scholar Password: xxxx PortNumber: 3306 ServerName: x.y.z.t Inside my glassfish3/glassfish/lib, I have my mysql-connector-java-5.1.13-bin.jar Inside the database, table mysql here is the result of the query select User, Host from user; +------------------+-----------+ | User | Host | +------------------+-----------+ | root | 127.0.0.1 | | debian-sys-maint | localhost | | root | localhost | | root | yunaeyes | +------------------+-----------+ Now from my machine, if I try to connect to this db via mysql browser (mysql client software), well I cant. Well from the table above, seem like it only allow localhost to connect to this db. Keep in mind that both my db and my GF are on the same VPS. Please help

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Convert a MSSQL database to MYSQL database

- by soldieraman

Alright so I want to convert an already exist MSSQL database (2005) to a MYSQL database. There is nothing extraordinary to be done The only things I need to achieve is Recreate the tables Transfer data Relationships would be nice but not necessary No views, no sprocs, no functions. Any easy way to do this. Also do you know of any DST (Database Synchronization Tool) which would let me do MSSQL to MYSQL MYSQL to MYSQL MSSQL to MSSQL (I know there is SQL Delta for this)

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What are appropriate ways to represent relationships between people in a database table?

- by Emilio

I've got a table of people - an ID primary key and a name. In my application, people can have 0 or more real-world relationships with other people, so Jack might "work for" Jane and Tom might "replace" Tony and Bob might "be an employee of" Rob and Bob might also "be married to" Mary. What's the best way to represent this in the database? A many to many intersect table? A series of self joins? A relationship table with one row per relationship pair and type, where I insert records for the relationship in both directions?

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Command line import of database using latin1 encoding

- by chrisjlee

I'm using a particular cloud hosting solution (one which i won't name) and they don't provide ssh access so i'm at a whim on how the database is dumped. I downloaded the dump which is packed into a tar.gz file. I discover that this file utilizes latin1 encoding. Which i don't get to specify the encoding for the host i'm using because i don't have SSH access or DB access. I try to import it via command line for my local development environment (mysql -uroot foodb < file.db) like i usually do with other databases but am having problems. Is it possible to import a database via command line by specifying which encoding (preferably latin1) before importing it? Or do i have to convert it to UTF8?

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Optimising Database Calls

- by Dwaine Bailey

I have a database that is filled with information for films, which is (in turn) read in to the database from an XML file on a webserver. What happens is the following: Gather/Parse XML and store film info as objects Begin Statement For every film object we found: Check to see if record for film exists in database If no film record, write data for film Commit Statement Currently I just test for the existence of a film using (the very basic): SELECT film_title FROM film WHERE film_id = ? If that returns a row, then the film exists, if not then I need to add it... The only problem is, is that there are many many hundreds of records in the database (lots of films!) and because it has to check for the existence of a film in the database before it can write it, the whole process ends up taking quite a while (about 27 seconds for 210 films) Is there a more efficient method of doing this, or just any suggestions in general? Programming Language is Objective-C, database is in sqlite3 Thanks, Dwaine

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Postgres: clear entire database before re-creating / re-populating from bash script

- by Hoff

hi folks, I'm writing a shell script (will become a cronjob) that will: 1: dump my production database 2: import the dump into my development database Between step 1 and 2, I need to clear the development database (drop all tables?). How is this best accomplished from a shell script? So far, it looks like this: #!/bin/bash time=`date '+%Y'-'%m'-'%d'` # 1. export(dump) the current production database pg_dump -U production_db_name > /backup/dir/backup-${time}.sql # missing step: drop all tables from development database so it can be re-populated # 2. load the backup into the development database psql -U development_db_name < backup/dir/backup-${time}.sql Many thanks in advance! Martin

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How to rename database without first stopping SQL instance to flush connections

- by John Galt

Is there a way to force a database into single user mode so a script can be run to rename databases? I find I have to Restart the instance of SQL (to force off any connections from a web app, etc.) and then I can run this script: USE master go sp_dboption MDS, "single user", true go sp_dboption StagingMDS, "single user", true go sp_renamedb MDS, LastMonthMDS go sp_renamedb StagingMDS, MDS go sp_dboption LastMonthMDS, "single user", false go sp_dboption MDS, "single user", false go After this script runs, I can restart IIS for my web app and it can connect to the new production database. All the above works well and we've been doing this for years but now we've upgraded to SQL 2008 and the SQL2008 instance also hosts other databases that support other web apps. So, rather than using a Restart of the whole SQL instance to enable subsequent single-user mode on 2 databases, is there a less intrusive way of accomplishing this? Thanks.

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Cannot start Oracle XE 11gR2 Net Listener and Database on Ubuntu 13.04

- by hydrology

I have been following the setup step on this article for installing Oracle XE 11g R2 on Ubuntu 13.04. The environment variables PATH, ORACLE_HOME, ORACLE_SID, NLS_LANG ORACLE_BASE have all been set up correctly. simongao:~ 06:16:38$ echo $PATH /usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/simongao/adt-bundle-linux-x86_64-20130219/sdk/platform-tools:/u01/app/oracle/product/11.2.0/xe/bin simongao:~ 06:18:36$ echo $ORACLE_HOME /u01/app/oracle/product/11.2.0/xe simongao:~ 06:23:29$ echo $ORACLE_SID XE simongao:~ 06:23:35$ echo $ORACLE_BASE /u01/app/oracle simongao:~ 06:23:37$ sudo echo $LD_LIBRARY_PATH /u01/app/oracle/product/11.2.0/xe/lib simongao:~ 06:23:48$ echo $NLS_LANG /u01/app/oracle/product/11.2.0/xe/bin/nls_lang.sh However, when I try to startup the service, I receive the following error information. simongao:~ 06:18:40$ sudo service oracle-xe start Starting Oracle Net Listener. Starting Oracle Database 11g Express Edition instance. Failed to start Oracle Net Listener using /u01/app/oracle/product/11.2.0/xe/bin/tnslsnr and Oracle Express Database using /u01/app/oracle/product/11.2.0/xe/bin/sqlplus.

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What are performance limits of a database?

- by Tommy

What are some rough performance limits (read/s, write/s) for a single database server (no master-slave architecture), assuming storage on disk? How many read/s, write/s, depending on the kind of disk? (SSD vs non-SSD) , assuming simple operations (select one row by primary key, update one row, correctly indexed). I assume this limit is dependent on disk seek/write. EDIT: My question is more about getting rough metrics of the number of operations a database supports: to be able to know for example, if a new feature triggering 300 inserts/s can be supported without scaling out with additional servers.

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Timeout Error in SQL Server Database Mail Feature

- by RedLEON

I configured database mail profile as gmail smtp server, SSL and port 465. I didn't restart server. And this is first time to use Database Mail feature on that server. When I send a testing mail it give me this error message: The mail could not be sent to the recipients because of the mail server failure. (The operation has timed out) I tried this mail configuration with Thunderbird and I could send messages througt this SMTP. Why is SQL Server giving this eror message? I searched here but didn't find any solution.

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Postgres pg_dump dumps database in a different order every time

- by behrk2

Hello, I am writing a PHP script (which also uses linux bash commands) which will run through test cases by doing the following: I am using a PostgreSQL database (8.4.2)... 1.) Create a DB 2.) Modify the DB 3.) Store a database dump of the DB (pg_dump) 4.) Do regression testing by doing steps 1.) and 2.), and then take another database dump and compare it (diff) with the original database dump from step number 3.) However, I am finding that pg_dump will not always dump the database in the same way. It will dump things in a different order every time. Therefore, when I do a diff on the two database dumps, the comparison will result in the two files being different, when they are actually the same, just in a different order. Is there a different way I can go about doing the pg_dump? Thanks!

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Connect android to database

- by danny

I am doing a school project where we need to create an android application which needs to connect to a database. the application needs to gain and store information for people's profiles on the database. But unfortunatly we are a little bit stuck at this point because there are numerous ways to link the application such as http request through apache or through the SOAP/REST protocol. But it's really hard to find good instructions or tutorials on the problem since I can't really find them. Maybe that's cause i'm probably using the wrong words on google. Unfortunately I have little relevant information. So if anyone can help me with finding relevant links to good online tutorials or howto's than those are very welcome.

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Storing n-grams in database in < n number of tables.

- by kurige

If I was writing a piece of software that attempted to predict what word a user was going to type next using the two previous words the user had typed, I would create two tables. Like so: == 1-gram table == Token | NextWord | Frequency ------+----------+----------- "I" | "like" | 15 "I" | "hate" | 20 == 2-gram table == Token | NextWord | Frequency ---------+------------+----------- "I like" | "apples" | 8 "I like" | "tomatoes" | 12 "I hate" | "tomatoes" | 20 "I hate" | "apples" | 2 Following this example implimentation the user types "I" and the software, using the above database, predicts that the next word the user is going to type is "hate". If the user does type "hate" then the software will then predict that the next word the user is going to type is "tomatoes". However, this implimentation would require a table for each additional n-gram that I choose to take into account. If I decided that I wanted to take the 5 or 6 preceding words into account when predicting the next word, then I would need 5-6 tables, and an exponentially increase in space per n-gram. What would be the best way to represent this in only one or two tables, that has no upper-limit on the number of n-grams I can support?

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Writing datatable to database file, one record at a time

- by Kevin

I want to write a C# program that will read a row from a datatable (named loadDT) and update a database file (named Forecasts.mdb). My datatable looks like this (each day's value is a number representing kilowatts usage forecast): Hour Day1 Day2 Day3 Day4 Day5 Day6 Day7 1 519 520 524 498 501 476 451 My database file looks like this: Day Hour KWForecast 1 1 519 2 1 520 3 1 524 ... and so on. Basically, I want to be able to read one row from the datatable, and then extrapolate that out to my database file, one record at a time. Each row from the datatable will result in seven records written to the database file. Any ideas on how to go about this? I can connect to my database, the connection string works, and I can update and delete from the database. I just can't wrap my head around how to do this one record at a time.

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- by GB_J

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- by Robert May

- by Trey Sargent

- by Paul Alan Taylor

- by kce

- by Josh

- by James

- by KThompson

- by Harry Pham

- by soldieraman

- by Emilio

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