rdbms | 易学教程

Migrating from 'native' OODBMS to ORM (Entity Framework / SQL Server)

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A while ago we started developing a new project which internally has about 25-30 different classes/types/models that are heavily related to each other either via 1:n, n:m or n:1 relationships. Back then we went with a native .net oodbms system basically because what it allowed us to do was to take our object model and simply add a few persistence related methods(-calls) here and there and we were ready to go. However, over time we ran into more and more caveats, really bad, non-fixable (within a reasonable timeframe) limitations that forced us to implement slow workarounds resulting in

What strategy to migrate data from a spreadsheet to an RDBMS?

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问题 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.

Is Ms Access DBMS Or RDBMS?

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问题 IS Ms Access DBMS or RDBMS? I also do Google to find answer of this question,but in some website or blog says it is DBMS while others are says it is RDBMS.. so what is correct answer? and Please understand why it is DBMS or RDBMS? 回答1: MS Access is a Relational Database Management System so therefore RDBMS , however you can use it in a non-relational fashion if you so wish so it can be used as a DBMS . 回答2: Short Answer : Both. Detail : Microsoft Access is a DBMS but also something more: a

Terribly slow SQL query with COUNT and GROUP BY on two columns

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问题 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 |

How do I create a (Type, ID) (aka 'polymorphic')- foreign key column in MS Access?

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RDBMS impact on Golang [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 5 years ago . I'm not going to make a big long rattle on this question about what I've tested and number crunching. I'm more interested in actual up-to-date practice performances. I've read tons of articles already and some of them are pretty skeptical or either very pro to one library . I

How do I migrate easily from MySQL to PostgreSQL?

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I'd like to migrate an existing MySQL database (around 40tables, 400mb data) to Postgres before it gets bigger. I searched the web and tried some migration-scripts (some of them can be found here ). None of them works seamlessly - if it would be just a few glitches I had to fix manually, it wouldn't be a problem, but the resulting dumps don't look like valid PostgreSQL at all. Did anybody succeed in migrating a production table without using a full workday - is there an easy solution to that problem? Note: I also would consider commercial products (as long as pricing is still feasible). In

hierarchical data in a database: recursive query vs. closure tables vs. graph database

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问题 I'm starting on a new project that has some hierarchical data and I'm looking at all the options for storing that in a database at the moment. I am using PostgreSQL, which does allow recursive querying. I also looked into design patterns for relational databases, such as closure tables and I had a look at graph database solutions such as neo4j. I'm finding it difficult to decide between those options. For example: given that my RDBMS allows recursive queries, would it still make sense to use

Why use primary keys?

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What are primary keys used aside from identifying a unique column in a table? Couldn't this be done by simply using an autoincrement constraint on a column? I understand that PK and FK are used to relate different tables, but can't this be done by just using join? Basically what is the database doing to improve performance when joining using primary keys? Mostly for referential integrity with foreign keys,, When you have a PK it will also create an index behind the scenes and this way you don't need table scans when looking up values RDBMS providers are usually optimized to work with tables

How to implement ONE-TO-MANY in a database

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问题 I want to implement one-to-many concept in my application. This is the scenario: I have two tables (i). Person(ID, NAME, AGE, DEPT) (ii). Person Responsibilities(ID, RESP'S) One person may have more than one responsibility. How shall I implement a 1-n relationship here? Actually, I don't understand the correct concepts for this. Any suggestions or links to understand this concept would be appreciated. 回答1: This one-to-many relationship can be interpreted in plain English like this... A Person