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  • Tutorials for .NET database app using SQLite

    - by ChrisC
    I have some MS Access experience, and had a class on console c++ apps, now I am trying to develop my first program. It's a little C# db app. I have the db tables and columns planned and keyed into VS, but that's where I'm stuck. I'm needing C#/VS tutorials that will guide me on configuring relationships, datatyping, etc, on the db so I can get it ready for testing of the schema. The only tutorials I've been able to find either talk about general db basics (ie, not helping me with VS/C#), or about C# communications with an existing SQL db. Thank you. (In case it matters, I'm using the open source System.Data.SQLite (sqlite.phxsoftware.com) for the db. I chose it over SQL Server CE after seeing a comparison between the two. Also I wanted a server-less version of SQL because this little app will be on other people's computers and I want to to do as little support as possible.)

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  • database datatype size

    - by yeeen
    Just to clarify by specifying sth like VARCHAR(45) means it can take up to max 45 characters? I rmb I heard from someone a few years ago that the number in the parathesis doesn't refer to the no of characters, then the person tried to explain to me sth quite complicated which i don't understand n forgot alr. And what is the difference btn CHAR and VARCHAR? I did search ard a bit and see that CHAR gives u the max of the size of the column and it is better to use it if ur data has a fix size and use VARCHAR if ur data size varies. But if it gives u the max of the size of the column of all the data of this col, isn't it better to use it when ur data size varies? Esp if u don't know how big is ur data size gg to be. VARCHAR needs to specify the size (CHAR don't really need right?), isn't it more troublesome?

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  • EAV Database Sheme

    - by GLO
    Hello Stackoverflow comunity! I believe that my question has to do with all db guru here! Do you know the EAV DB Scheme ( http://en.wikipedia.org/wiki/Entity-attribute-value_model ) and what they say about the performing of this model. I wonder, If I break this model into smaller tables what the result is? Let's talk about it. I have a db with more that 100K records. A lot of categories and many items ( with different properties per category ) Everything is stored in a EAV. If I try to break this scheme and create for any category a unique table is something that will I have to avoid? Yes, I know that probably I'll have a lot of tables and I'll need to ALTER them if I want to add an extra field, BUT is this so wrong? I have also read that as many tables I have, the db will be populate with more files and this isn't good for any filesystem. Any suggestion? Thank you!

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  • EF4 cross database relationships

    - by Daniel
    Hello all, I was wondering if EF4 support cross-databse relationships? For instance: db1 Author Id Name db2 Posts Id Content db1.Author.Id What ideally I need to do to get this relation in my ef4 model? Do you guys have any idea? Thanks

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  • c# reading integer fields from database, returning empty string when reading integer type field

    - by arnoldino
    what is wrong with this code? field="id"; table="MInvMonth"; condition="machine_id=37"; public static String getConditionedField(String field, String table, String condition) try { if (cmd == null) getConnection(); cmd.CommandText = "Select " + field + " from " + table + " where " + condition; SQLiteDataReader reader = cmd.ExecuteReader(); if (reader.HasRows==true) { reader.Read(); string s = reader[0].ToString(); // return first element reader.Close(); return s; } reader.Close(); return null; } catch (Exception e) { MessageBox.Show("Caught exception: " + e.Message+"|"+cmd.CommandText); return null; } I checked the sql statement, it turns the right value. why can't I read it? the returnvalue is "".

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  • What relational database innovations have there been in the last 10 years

    - by Simon Munro
    The SQL implementation of relational databases has been around in their current form for something like 25 years (since System R and Ingres). Even the main (loosely adhered to) standard is ANSI-92 (although there were later updates) is a good 15 years old. What innovations can you think of with SQL based databases in the last ten years or so. I am specifically excluding OLAP, Columnar and other non-relational (or at least non SQL) innovations. I also want to exclude 'application server' type features and bundling (like reporting tools) Although the basic approach has remained fairly static, I can think of: Availability Ability to handle larger sets of data Ease of maintenance and configuration Support for more advanced data types (blob, xml, unicode etc) Any others that you can think of?

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  • browse data in Android SQLite Database

    - by Justin C
    Is there a way for an Android user to browse the SQLite databases on his/her phone and view the data in the databases? I use the SoftTrace beta program a lot. It's great but has no way that I can find to download the data it tracks to a PC. Thanks

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  • Source Controlled Database Data import strategies.

    - by H. Abraham Chavez
    So I've gotten a project and got the db team sold on source control for the db (weird right?) anyway, the db already exists, it is massive, and the application is very dependent on the data. The developers need up to three different flavors of the data to work against when writing SPROCs and so on. Obviously I could script out data inserts. But my question is what tools or strategies do you use to build a db from source control and populate it with multiple large sets of data?

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  • Auto Reconnect of Database Connection

    - by wesley
    I have a DBCP connection pool in Tomcat. The problem is that when the connection is lost briefly the appliction is broken because DBCP won't try to reconnect again later when there is a connection. Can I get DBCP to reconnect automatically?

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  • Database best practices

    - by user270797
    I have a table which stores comments, the comment can either come from another user, or another profile which are separate entities in this app. My original thinking was that the table would have both user_id and profile_id fields, so if a user submits a comment, it gives the user_id leaves the profile_id blank is this right, wrong, is there a better way?

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  • mysql database normalization question

    - by Chocho
    here is my 3 tables: table 1 -- stores user information and it has unique data table 2 -- stores place category such as, toronto, ny, london, etc hence this is is also unique table 3 -- has duplicate information. it stores all the places a user have been. the 3 tables are linked or joined by these ids: table 1 has an "table1_id" table 2 has an "table2_id" and "place_name" table 3 has an "table3_id", "table1_id", "place_name" i have an interface where an admin sees all users. beside a user is "edit" button. clicking on that edit button allows you to edit a specific user in a form fields which has a multiple drop down box for "places". if an admin edits a user and add 1 "places" for the user, i insert that information using php. if the admin decides to deselect that 1 "places" do i delete it or mark it as on and off? how about if the admin decides to select 2 "places" for the user; change the first "places" and add an additional "places". will my table just keep growing and will i have just redundant information? thanks.

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  • VS2008 adding SQL Server Database (SQL Server 2008 Mgmt Studio) not working

    - by Kahn
    I'm trying to practice using the ASP.Net MVC at home, but I ran into an impossible problem. I cannot open a connection to SQL Server 2008, I get this error: "Connections to SQL Server files (*.mdf) require SQL Server Express 2005 to function properly. ..." I've googled around for numerous responses, none of them either working or addressing this issue. I'm running Vista 32bit, my SQL Server 2008 Mgmt Studio is also 32bit, I have SP1 installed both on VS2008 Professional, as well as the SQL Server. I changed the machine.config connectionStrings from ./SQLExpress to my SQL Server 2008 name. Now if I connect manually through web.config, in an asp:datasource or code-behind, everything works fine. But for some reason trying to add a DB Connection directly like this always gets the error. This is pretty fatal, since I can't rightly do much unless I can use LINQ to SQL with my MVC test project, and this is the only way I know how. Worked fine in school and work, but not at home. Installing SQL Server Express 2005, as some have suggested, is not an option. Obviously it HAS to work with SQL Server 2008. Thanks in advance.

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  • Reverse engineer an ORM

    - by Oren Mazor
    Given a [mysql] database with a given schema, is it possible to generate an ORM interface for it? doesn't matter if its php, python or perl. in other words, I have a database and I have to ask it a few questions. while I could just craft a bunch of SQL queries (okay, several dozen), this is way more interesting to think about. is this a valid question, even? I have no design background with ORMs, but I've used a few (django's, symfony's, etc).

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  • Getting-started: Setup Database for Node.js

    - by Emile Petrone
    I am new to node.js but am excited to try it out. I am using Express as a web framework, and Jade as a template engine. Both were easy to get setup following this tutorial from Node Camp. However the one problem I am finding is I can't find a simple tutorial for getting a DB set up. I am trying to build a basic chat application (store session and message). Does anyone know of a good tutorial? This other SO post talks about dbs to use- but as this is very different from the Django/MySQL world I've been in, I want to make sure I understand what is going on. Thanks!

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  • String Field Sizes for unicode database fields using different data access components

    - by Serg
    mjustin in his question 1 and question 2 says that TWideStringField.Size property for UTF8 fields in Delphi 2009 dbExpress is 4 times larger than the logical field size (max number of characters in the field). I inclined to consider this a dbExpress bug. That is what Delphi 2009 Help says: The interpretation of Size depends on the data type. The meaning of Size for data types that use it is given in the following table. For all other data types, Size is not used and its value is always 0. ftString - Size is the maximum number of characters in the string. I am using FibPlus 6.9.9 and it follows the above documentation - the string field size is the maximum number of characters, not bytes. So the question also implies the following question: Are DbExpress drivers in Delphi 2009 unusable for unicode databases?

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  • close fails on database connections (managed connection cleanup fails) in websphere 7 but not in web

    - by mete
    I have a simple method (used in a web application through servlets) that gets a connection from a JNDI name and issues a select statement (get connection, issue select, return result, close the connection etc. in finally). Due to other methods in the application the connection is set as autocommit=false. This method works normally in websphere 6.1 as well as in glassfish and weblogic. However, in websphere 7, it receives cleanup failed error when I close the connection because, it says, the connection is still in a transaction. Because I was not updating anything I did not commit or rollback the connection in this method (which can be wrong). If I add commit before closing the connection, it works. My question is why it works in websphere 6.1 (and other containers) and why not in websphere 7 ? What can be the cause of this difference ?

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  • Does a version control database storage engine exist?

    - by Zak
    I was just wondering if a storage engine type existed that allowed you to do version control on row level contents. For instance, if I have a simple table with ID, name, value, and ID is the PK, I could see that row 354 started as (354, "zak", "test")v1 then was updated to be (354, "zak", "this is version 2 of the value")v2 , and could see a change history on the row with something like select history (value) where ID = 354. It's kind of an esoteric thing, but it would beat having to keep writing these separate history tables and functions every time a change is made...

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  • Why would you want a case sensitive database?

    - by Khorkrak
    What are some reasons for choosing a case sensitive collation over a case insensitive one? I can see perhaps a modest performance gain for the DB engine in doing string comparisons. Is that it? If your data is set to all lower or uppercase then case sensitive could be reasonable but it's a disaster if you store mixed case data and then try to query it. You have then apply a lower() function on the column so that it'll match the corresponding lower case string literal. This prevents index usage in every dbms. So wondering why anyone would use such an option.

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  • What ports does Advantage Database Server need?

    - by asherber
    I have an application which uses ADS and I am attempting to deploy it in a Windows network environment with a rather restrictive firewall. I am having a problem configuring firewall ports appropriately. ADS lives on \server, and it's listening on port 1234. When \client tries to connect to \server\tables, I get Error 6420 (Discovery process failed). When \client tries to connect to \server:1234\tables, I get error 6097, bad IP address specified in the connection path. \server is pingable from \client, and I can telnet to \server:1234. If I try to connect from a client machine inside the firewall, either connection path works fine. It seems there must be something else I need to open in the firewall. Any ideas? Thanks, Aaron.

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  • mysql partitioning

    - by Yang
    just want to verify that database partition is implemented only at the database level, when we query a partitioned table, we still do our normal query, nothing special with our queries, the optimization is performed automatically when parsing the query, is that correct? e.g. we have a table called 'address' with a column called 'country_code' and 'city'. so if i want to get all the addresses in New York, US, normally i wound do something like this: select * from address where country_code = 'US' and city = 'New York' if now the table is partitioned by 'country_code', and i know that now the query will only be executed on the partition which contains country_code = US. My question is do I need to explicitly specify the partition to query in my sql statement? or i still use the previous statement and the db server will optimize it automatically? Thanks in advance!

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  • Recreation of MySQL DB using "mysql mydb < mydb.sql" is really slow when the table has tens of milli

    - by Jian Lin
    It seems that a MySQL database that has a table with tens of millions of records will get a big INSERT INTO statement when the following mysqldump some_db > some_db.sql is done to back up the database. (is it 1 insert statement that handles all the records?) So when reconstructing the DB using mysql some_db < some_db.sql then the CPU is hardly busy (about 1.8% usage by the mysql process... I don't see a mysqld either?) and also the hard disk doesn't seem to be too busy... Last time, the whole restore process took 5 hours. Is there a way to make it faster? Such as, when doing mysqldump, can it break the INSERT statement into shorter ones, so that the mysql doesn't need to parse the line so hard when restoring the DB?

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