Programming Games in Visual Basic: Data base

1
Programming Games in Visual Basic Data base

• Catch up questions
• Data base generalities specifics on Visual
  Basic links
• Lab work on projects.

2
Questions?

• Hangman
• word bank is an array of strings
• Dynamically loading alphabet (label control
  array)
• String operations
• Cannonball
• moving ball (setup in Fire button Click, movement
  checking for hitting target or ground in timer)
• press button drag

3
Suggestions

• Reflect back on a project. What was difficult?
  What was similar to another project?
• Similarities differences between projects
• Use of images in memory versus mixed hangman
• Use of Booleans (flags) for firstturn follow-up
  in chance, first and second turns in memory
• Clicking on labels
• Data in labels (memory) versus internal variables
• Counting matches in memory matches in hangman
  turns in hangman
• ?

4
Data base terminology

• is a collection of files. A data base management
  system (DBMS) is a software application for
  creating modifying databases and for producing
  report.
• Database
• Tables
• Records (rows)
• Fields (attributes, columns)

5
Example (simpler than in quiz)

• Table the questions
• A question holds
• Text of question
• Answer
• Value
• Category
• So, in the simple case 4 fields 4 attributes.
  Datatype of 1st and 2nd and 4th field is text.
  Datatype of 3rd field is number.

6
Data base terminology, cont.

• A query is a request for information from a data
  base.
• SQL (structured query language) is the standard
  for queries to a data base.
• Select from questions where category trivia
• Get the whole record (all attributes) from all
  the records from the questions table in which the
  category attribute equals trivia
• Select question, answer from questions where
  used false
• Get the question and answer attributes from the
  questions table in which the used attribute is
  false
• Select distinct category from archive
• Get all the distinct (no duplicate) values of the
  category attribute

7
Advanced Warning

• Visual Basic statements involving Select
  statements have complex syntax
• A string containing the Select statement is sent
  to the database.
• The string may be made by concatenating strings
  and the value of variables.
• There may be single quotation marks and double
  quotation marks.
• Long statements may need to be continued on the
  next line, requiring an underscore _

8
Quiz project

• VB to DB connection for
• Controls on quiz form and DB edit form
• Set properties in the data control
• Generating list of categories
• Generate a special recordset with just one field
• Generating list of non-used questions within a
  specific category
• Generate a recordset for the controls. Use Rnd
  to advance the cursor to a random choice within
  this set.

9
Setting up VB to database connections

• Connecting data control to the database and the
  table (there is only one) in the database
• dbQuestions.DatabaseName App.Path "/quiz.mdb"
• dbQuestions.RecordSource "archive"
• In the eventhandler for setting up the list of
  categories
• Dim dbQuestions as DataBase
• Dim rst as Recordset
• Set dbQuestions OpenDatabase(App.Path
  "/quiz.mdb")
• Set rst _
• dbQuestions.OpenRecordset("Select distinct
  category from archive")

10
Example of query

• Note your code has already set up dbQuestions as
  the link to the database.
• dbQuestions.RecordSource "Select from " _
• "archive where category '" strCat _
• "' And " _
• "used 0
• The words
• Select from archive where category
• are taken literally. Then it is combined with the
  value of strCat and then the literal
• And used 0
• The single quotation marks will surround the
  actual value in the variable strCat (namely the
  selected category).

11
Visual Basic / Data base

• Data control
• at design time or run time, specify database AND
  table
• Database aware controls
• link to the data control AND link to specific
  field

12
Click then select database
Choose table in database
13
When the pulldown was clicked, the menu shows
the only data control.
Field in table in database
14
Visual Basic / database

• Recordset is set (sequence) of records!
• Implicit notion of the current record. This can
  be changed
• movefirst
• movenext
• moveprev

15
Recordsets

• Can be associated with a data control and
  controls on the form
• OR
• can be independent of data control (and controls
  on the form)

16
Quiz project

• Database is one table, named questions
• A question is a record in the table.
• Question includes the following fields
• Question text
• two model answers (more on this later)
• Point value (may be set as currency)
• category
• used switch (yes/no)

17
Comparing strings to patterns

• Various ways of using special characters for
  patterns.
• The patterns suggested in the text use just the
  wild card character
• If strAns Like strModel then
• If strAns holds Christopher Columbus and
• strModel holds Columbus then the Like operator
  will return true
• Consult HELP for more possibilities

18
Homework/Lab

• Continue with projects
• Read text
• Note chapter 7 / Quiz show is one of the
  'advanced' projects.
• Your own project can be enhancement of one of the
  6 projects, one of the advanced projects or an
  existing game or something totally of your own
  design.