An eLearning database portal of the UAS-Cologne

Our online portal EDB has a new design and new integrated features! You can find MC test, SQL trainer and some other interactive tools consolidated with uniform user administration and chat functionality! Join in! For use of edb a user authentication setup is required. The Intention of this web application is to support students and readers, who wants to deal with data bases. Read more...

Registration

In order to be able to use the web application you have to register first and login with your user name and your password. You can register here: register, if you still not have a user identification. Please enter a valid e-mail address. The user name and the e-mail address have to be clear in the database.

Partnership

We thank all supporters of our project edb and for this we provided a partnership side. Partnership

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The target of the SQL-Trainer is to develop correct phrasings for SELECT requests. Queries that have been selected randomly will be asked from approx. 200 questions. The results are than compared with the results of the sample solutions. The program sends the queries to an Oracle database to be processed and there they are answered. A SELECT query is accepted as correct, when the result of the query coincides in the quantities with the result of the sample solution.

Select first a database schema and a level of difficulty! (for football fans: the database schema "football" contains the complete data of the world cup of 2006).

• The program sends your queries for their accomplishment to an Oracle database and there they are accomplished.
• In the case that you want to see the relations of the used database scheme you can view the correspondent PDF file. Below the link "Tables" is hidden the content of the used database relations.
• A SELECT query is accepted as correct, when the result of the query coincides in the quantities with the result of the sample solution. Therefore it does not have to be exactly the same SQL instruction, it has to be only an instruction with the same quantity in the result. For this reason it is important to insert in your SELECT query the columns in the sequence that has been preset in the task definition.
• In the case that you have a SQL syntax error or a semantic error, the program will emit an Oracle error message. Therefore you can correct the wrong instruction with the back button. Since SQL is not case sensitive the SQL key words in this test are not sensitive neither.
• In the case that you can not solve a task, click the button "next task".After finishing the test you will see all sample solutions.

The application has been developed by the students Juri Bauer, Alex Maier and Alexander Peters.

With the SQL-Trainer2 you can rehearse in addition to SELECT queries other DML instructions, i. e. INSERT, UPDATE and DELETE.

The program can be used like the SQL-TRAINER.

The application has been developed by Jan Philipp and Andre Kapser.

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In six steps to the third normal form: A further difficulty of data modelling is the normalization of a relational schema. The 3NF-Trainer demonstrates how you can normalize a relation interactively up to the 3rd normal form (3NF). The algorithm is divided into single steps and after each step the correct solution with an intermediate result is shown as well as your rating points for your solution.

The six steps are the following: A 3NF-Task with the associated table is randomized from a set of tasks store in a Data Base.

1. Step 1 and 2 consist of deciding (yes/no selection) whether the table already is in first normal form. If not, in the second step you have to drop the columns into a drag&drop field, which are not in first normal form. Afterwards the table is transferred automatically into the first normal form.
2. Step 3: Now you determine all functional dependencies. You can drop the columns in a corresponding drag&drop field (primary keys - > values)
3. Step 4: For next step please choose by drag&drop those columns, which indicates a primary key.
4. Step 5: Now you transform the 1NF-table into a 2NF-table. For this as in the previous steps the columns of the table can be dropped in a drag&drop field.
5. Step 6: Now you transform the 2NF-tables into 3NF-tables. This step consists like step 5 of drag&drop fields, in which you can drop the columns.

At the end of a 3NF training the sample solutions and your reached scores are shown

All sample solutions are administrated database driven. If you have any questions or you noticed any error, please contact the edb administrators.

The 3NF-Trainer was developed by Andre Kasper and Marc Kastleiner as a project influenced by the diploma thesis of David Krievec.

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In addition to the data exchange, the data management of XML documents in databases is gaining more importance in the XML environment. How can the query on XML documents be more efficient? XPATH and XSLT offer only very limited possibilities. The query language XQuery closes this gap und is treated as the replacement language of the SQL or it is treated on the same level than the SQL. Instead of a SELECT-query a FLOWR-expression on a XML-Document is applied. It is surely not fortuitous that F = For, L = Let , O = Order By , W = Where and R = Return can be read in a similar way as a SELECT instruction.

An extensive implementation of the SQL/XML-Standard in the Oracle environment is available with Oracle XMLDB which can analyse even FLOWR expressions against elements of the type XMLTYPE thanks to the function XQUERY (expression). The basis for this is the object related data type XMLType of Oracle, which also assists the XQuery functionality. For this reason it is appropriate to test the new XML language. The XQuery trainer uses this functionality to facilitate the practice of FLOWR expressions.

From a pool of reformulated queries a question is selected randomly. This question has to be answered during the test in XQuery. At the beginning you should check the settings for the test in the XQuery-Trainer. Here you can set up the level of difficulty, the scheme and the task type (at the moment FLOWR/SELECT is only possible).

As soon as the test starts a question is selected randomly one which corresponds to the selected level of difficulty and to the XML scheme . The program sends the automatic formulated FLOWR expressions to an Oracle database for the processing and executes them there. In the case that the result of your FLOWR query coincides with the result of a sample solution that is saved in the database, the question is evaluated as correct.

The correspondent XML documents can be displayed in the same way as the sample solution. You can also abort a query and view the statistics (tasks that have been solved).

In addition the XQuery-Trainer offers an other XQuery-Sandbox for the practice with free FLOWR expressions.

The application has been developed by Michael Ipsen, Andre Kasper, Jan Philipp and Norbert Schneider.

A B-tree is a data or an index structure, which is used frequently in data bases and file systems. It is completely balanced and stores data sorted according to keys. Inserting, searches and deletion of data in B-trees are in amortize logarithmic time possible. B-trees grow differently than most search trees from the sheets to the root. (Source: Wikipedia)

This JAVA applet demonstrates inserting and searching of keys in the data structure. For clarity, for the input size of the type k are only values between 1 and 3 allowed. With the type k the maximum number of values and child nodes can be computed: 2*k-key values for each node can be stored and maximally 2*k+1-references can point to child nodes.

With large B-trees the scrollbar must be used to see the tree completely. In the status bar different information can be found, e.g. how many values are contained in the B-tree.

Create a tree

With the slider in the left corner you can produce a B-tree with the values K=1-3. After you clicked on Create BTree, you will get the feedback BTree created with K=.. in the status bar.

Inserting values

Values can be inserted within the range of 1 to 999. For this there is the possibility to enter the numbers manually and confirm this with one clicks on Insert or with the enter key. With larger trees it is annoying to enter the numbers by hand. For this there is the button Insert random. With one click a random number is inserted into the tree. Newly inserted values are marked red in the tree.

Deleting values

Existing values can be deleted also from a B-tree. The nodes are merged or balanced, if there are too little values in the tree. The attempt to delete a missing value leads to an error message in the status bar of the application.

Searching for values

If you enter a number and click on the button "Search", the search starts. If the value is found, the way is marked yellow there. If the value is not found a status message "Can't find Value" is shown.

This B-tree-applet was create by Reiner Hoppe, Jan Kuznik, Bernd Prizkau, Björn Rockstroh, Michael Seel and Ibrahim Kaciran.

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SQL-Sandbox

With the SQL Sandbox exists the possibility of writing own SQL statements and it will show you the result set. If it is a DML statement the sandbox shows you the result set before and after the execution of the statement. It is also an extension of the two SQL trainer. For this you can enter an ID of the current question, whereby the result of the sample solution is shown. So the own result set can be compared with the result set of the sample solution.

All DQL and DML statements can be tested. The existing patterns resemble the patterns of the SQL trainer.