rdbms

For example if I have an auto-numbered field, I add new records without specifying this field and let DB engine to pick it for me. So, will it pick the number of the deleted record? If yes, when? // SQL Server, MySQL. // Follow-up question: What happens when DB engine runs out of numbers to use for primary keys? NO. numerical primary keys will not reused, except you specify them manually(you should really avoid this!) AFAIK, this could happen in MySQL: How AUTO_INCREMENT Handling Works in InnoDB : InnoDB uses the in-memory auto-increment counter as long as the server runs. When the server is

In my project, where I'm the lead developer, we earlier had a network configuration that was stored a single XML file. The configuration contains info about a network layout - its constituent hosts, various details about each host like OS, platform, users configured in each them, several attributes for each user and so on. In the forthcoming version of the product, we want to move the data into a database of some sort since the configuration will be expanded to include more elements and details and maintaining them in XML files will start becoming cumbersome. The first choice was an RDBMS.

Is there an ORM-analogue for querying OLAP cubes / data-warehouses? I'm specifically interested in the .NET world, but generally interested in anything ;-) I've started an open source project, Kona, to wrap the ADOMD.Net lib, and try to bring ADOMD.Net into the 21st Century. You can get it up at http://www.codeplex.com/kona , but it does need some more love and attention. The task of converting lambdas to MDX isn't a small one, so I haven't even tried to to that, yet. I've tried to encourage MSFT to write a LINQ to MDX provider, but considering how few .Net developers are actually trying to

In this database, key1 & key2 make up the composite primary key of table4 , but i'm able to add a foreign key to table3 that comprise just key1 . Why MySQL allows this? Does the above database design make no sense at all? TL;DR It's not standard SQL. MySQL documentation itself advises not doing it. In SQL a FOREIGN KEY declaration must reference a column list declared PRIMARY KEY or UNIQUE NOT NULL. (PRIMARY KEY creates a UNIQUE NOT NULL constraint.) (The constraint has to be explicit, even though any set of NOT NULL columns containing a set that is UNIQUE has to be unique.) The MySQL

I am designing DATABASE for a Sales and Purchase application like ERP and using MYSQL as RDBMS, I have doubt on creating table for sales and purchase entities to go with single table for each module(Sale/Purchase) or multiple tables for each entities(Sales order, Sale invoice, Sale return, Purchase order, Purchase invoice, Purchase return) in longer run. Below is my use case. My application will have Sale Order, Sale Delivery, Sale Invoice, Sale Return and Credit Note and same entity for Purchase module also and all these entity may be enter linked in there module. Like Sale Order can be

This is linked to my other question when to move from a spreadsheet to RDBMS Having decided to move to an RDBMS from an excel book, here is what I propose to do. The existing data is loosely structured across two sheets in a work-book. The first sheet contains main record. The second sheet allows additional data. My target DBMS is mysql, but I'm open to suggestions. Define RDBMS schema Define, say, web-services to interface with the database so the same can be used for both, UI and migration. Define a migration script to Read each group of affiliated rows from the spreadsheet Apply validation

In Ruby-on-Rails, this is called a "polymorphic association." I have several Commentable things in my application, the tables for each are below: Post id | title | text | author (FK:Person.id) | ... Person id | name | ... Photo id | title | owner (FK:Person.id) | path | ... I'd like to add a Comments table as follows: Comments id | commentable_type | commentable_id | text | author (FK:Person.id) I understand that I lose the database's referential integrity this way, but the only other option is to have multiple Comments tables: PostComments , PersonComments , PhotoComments , ... And now for

I'm archiving this web forum, which normally gets purged about once a week. So I'm screen scraping it, and storing it into my database (PostgreSQL). I also do a little analysis on the data, with some graphs for users to enjoy, like what time of day is the forum most active, and so forth. So I have a posts table, like so: Column | Type ------------+------------------------------ id | integer body | text created_at | timestamp without time zone topic_id | integer user_name | text user_id | integer And I now want to have a post count for each user, for my little top 10 posters table. I came up