Multiple Tables (& foreign keys)

Blog Task 1

1. What does a column in a table represent?

    Field

2. What does a row in a table represent?

    Record

3. What does DBMS stand for?

    Database Management Systems

4. What is a primary key in a table used for?

    Primary key is used to identify each record. This field is usually the ID field and can be used to link
    records across multiple tables.

5. Why is the ID column such a useful field?

    To identify fields

6. What Access data type would you use to store the string “18 Segway Drive, Moonville” ?

    Text

7. What Access data type would you use to record True/False values?

     Yes/No

8. What Access data type would you use to store a number?

     Number

9. What Access data type would you use to store a long string such as an essay or report?

    Memo

10. A database is a collection of what?

     A collection of related data in a structured format (such as text, memo, number,

      Date/Time, Currency, Yes/No..etc.)

11. A table is made up of what?

      Rows and columns (Records and Fields)

12. What is a record?

     The rows in a table  

13. Are spaces allowed in field names?

      Yes, but it is not best practive

DatabaseScreenshot

The Object class

* What is the purpose of the Object class? 

Supports all classes in the .NET Framework class hierarchy and provides low-level services to derived classes. This is the ultimate base class of all classes in the .NET Framework; it is the root of the type hierarchy.

* How many constructors does it contain?

   One

* How many methods does it contain? 
   eight

* What is the purpose of the ToString method? 

   to get a string of the current object

Types of errors

Syntax error
Syntax errors (violations of the rules of a programming language)
A syntax error occurs when the Visual Basic compiler cannot understand a statement that you have written. Syntax errors can also occur when statements do not appear in the order.
Eg: A Procedure block cannot appear directly within a Namespace block. If an application has syntax errors, the application cannot be compiled. As a result, the program cannot be executed.


Run-time errorRuntime errors are not detected when a project is compiled. Rather, run-time errors occur as an application executes and an exception is thrown.
Eg: if some fields are updated in a trigger and a run-time error occurs while other fields have not been updated. When a trigger is entered, a write transaction begins. If a run-time error occurs inside the trigger, the write transaction is rolled back and the execution of the trigger is terminated.

Logic errorA program logic error is an error in an application that compiles and runs without causing run-time errors, but fails to function as intended.A logic error occurs when an application runs but produces incorrect results.
Eg:  if you intended to compute the area of a rectangle, you would multiply the length of the rectangle by its width. If you divided the numbers instead of multiplying, the application would produce an incorrect answer, creating a logic error.

What types of errors does the 'Error List' window display?
Syntax errors

String Manipulation

1. StrComp Method

 
Returns -1, 0, or 1, based on the result of a string comparison. 

Syntax:
Public Shared Function StrComp ( _
    String1 As String, _
    String2 As String, _
    Compare As CompareMethod _
) As Integer


Parameters:
String1
    Type: System.String
    Required. Any valid String expression.

String2
    Type: System.String
    Required. Any valid String expression.

Compare
    Type: Microsoft.VisualBasic.CompareMethod
    Optional. Specifies the type of string comparison. If Compare is omitted, the Option Compare

setting determines the type of comparison.


Return Value
Type: System.Int32
The StrComp function has the following return values.

If   
StrComp returns
String1 sorts ahead of String2 (-1)
String1 is equal to String2 (0)
String1 sorts after String2 (1)
   
Exception:
ArgumentException is the exception thrown by this function.(Condition: Compare value is not valid.)

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2. StrConv Method

Returns a string converted as specified

Syntax:
Public Shared Function StrConv ( _
    str As String, _
    Conversion As VbStrConv, _
    LocaleID As Integer _
) As String

Parameters:
str
    Type: System.String
    Required. String expression to be converted.

Conversion
    Type: Microsoft.VisualBasic.VbStrConv
    Required. VbStrConv member. The enumeration value specifying the type of conversion to

perform.

LocaleID
    Type: System.Int32
    Optional. The LocaleID value, if different from the system LocaleID value. (The system

LocaleID value is the default.)

Return Value:
Type: System.String
Returns a string converted as specified.
Exceptions
Exception     Condition

Exception:
ArgumentException is the exception thrown by this function.(Condition: Unsupported LocaleID, Conversion < 0 or > 2048, or unsupported conversion for specified locale.)

_____________________________________________________________________

3. InStrRev Method
 
Returns the position of the first occurrence of one string within another, starting from the right side of the string.

Syntax:
Public Shared Function InStrRev ( _
    StringCheck As String, _
    StringMatch As String, _
    Start As Integer, _
    Compare As CompareMethod _
) As Integer

Parameters:
StringCheck
    Type: System.String
    Required. String expression being searched.

StringMatch
    Type: System.String
    Required. String expression being searched for.

Start
    Type: System.Int32
    Optional. Numeric expression setting the one-based starting position for each search, starting from the left side of the string. If Start is omitted then –1 is used, meaning the search begins at the last character position. Search then proceeds from right to left.

Compare
    Type: Microsoft.VisualBasic.CompareMethod
    Optional. Numeric value indicating the kind of comparison to use when evaluating substrings.

If omitted, a binary comparison is performed. See Settings for values.

Return Value
Type: System.Int32
If   
InStrRev returns
StringCheck is zero-length (0)
StringMatch is zero-length (Start)
StringMatch is not found (0)
StringMatch is found within StringCheck (Position at which the first match is found, starting with the right side of the string.)
Start is greater than length of StringMatch (0)

Exception:
ArgumentException is the exception thrown by this function. (Condition: Start = 0 or Start < -1.)
_______________________________________________________________________


4. StrReverse Method
Returns a string in which the character order of a specified string is reversed.
Syntax:
Public Shared Function StrReverse ( _
    Expression As String _
) As String

Parameters:
Expression
    Type: System.String
    Required. String expression whose characters are to be reversed. If Expression is a zero-

length string (""), a zero-length string is returned.

Return Value:
Type: System.String
Returns a string in which the character order of a specified string is reversed.


Exception:
ArgumentException is the exception thrown by this function.

_________________________________________________________________


5. Space Method

Returns a string consisting of the specified number of spaces.

Syntax:
Public Shared Function Space ( _
    Number As Integer _
) As String


Parameters:
Number
    Type: System.Int32
    Required. Integer expression. The number of spaces you want in the string.

Return Value:
Type: System.String
Returns a string consisting of the specified number of spaces.

Exception:
ArgumentException is the exception thrown by this function. (Condition: Number < 0.)

_____________________________________________________________________


6. StrDup Method (int32,Char)

Returns a string or object consisting of the specified character repeated the specified number of times.

syntax:


Public Shared Function StrDup ( _
    Number As Integer, _
    Character As Char _
) As String

Overload List of StrDup Method (int32,Char)
* StrDup(Int32, Char)     Returns a string or object consisting of the specified character repeated the specified number of times.

Parameters:

Number
    Type: System.Int32
    Required. Integer expression. The length to the string to be returned.

Character
    Type: System.Char
    Required. Any valid Char, String, or Object expression. Only the first character of the

expression will be used. If Character is of type Object, it must contain either a Char or a

String value.

Return Value:
Type: System.String
Returns a string or object consisting of the specified character repeated the specified number of times.


Exceptions:
*ArgumentException (Condition: Number is less than 0 or Character type is not valid.)
*ArgumentNullException (Condition: Character is Nothing.)

Blog Tasks: Exceptions

4. How to: Use the Try/Catch Block to Catch Exceptions
What is a Try/Catch block?
Place the sections of code that might throw exceptions in a try block and place code that handles exceptions in a catch block. The catch block is a series of statements beginning with the keyword catch, followed by an exception type and an action to be taken.
The try-catch statement consists of a try block followed by one or more catch clauses, which specify handlers for different exceptions. When an exception is thrown, the common language runtime (CLR) looks for the catch statement that handles this exception. If the currently executing method does not contain such a catch block, the CLR looks at the method that called the current method, and so on up the call stack. If no catch block is found, then the CLR displays an unhandled exception message to the user and stops execution of the program.

Blog Tasks: Exceptions

3. Exception Hierarchy
What are the names of the 2 exception type categories?*The pre-defined common language runtime exception classes derived from SystemException.
*The user-defined application exception classes derived from ApplicationException..

When is a IndexOutOfRangeException thrown?
Thrown by the runtime only when an array is indexed improperly.

Blog Tasks: Exceptions

2. The Exception class.
What is the purpose of the class?
To slove ArithmeticException errors and DivideByZeroException errors.

What class does it directly inherit from?
exception classes inherit directly from exception

How many constructors are available for this class?
Four

Blog Tasks: Exceptions

1. Exceptions
What is an exception?
Exception represents errors that occur during application execution. Exceptions can be thrown for several reasons, such as dividing a number by a zero and numeric overflow.

Week 4 - Exception Handling

Week 4 - Exception Handling

3. Research the Len, InStr & Mid functions.

Len Function

Returns the number of characters of the specified string expression, excluding trailing blanks

Syntax    LEN ( string_expression )

               

Arguments

string_expression 

string_expression can be a constant, variable, or column of either character or binary data

Return Types

bigint if expression is of the varchar(max), nvarchar(max) or varbinary(max) data types; otherwise, int.

5. HashTable

* Include a link to the HastTable documentation at MSDN

http://msdn.microsoft.com/en-us/library/system.collections.hashtable.aspx

5. HashTable

    * What is a HashTable?

A Hashtable is used in Java to create a hash structure - that is, a structure with key-value pairs. To create a HashTable, one calls the constructor:

HashTable ht = new HashTable();

    * What is a key/value pair?

A key-value pair (KVP) is a set of two linked data items: a key, which is a unique identifier for some item of data, and the value, which is either the data that is identified or a pointer to the location of that data. Key-value pairs are frequently used in lookup tables, hash tables and configuration files.

4. Sequence Diagrams

What is a Sequence diagram & what does it communicate?

UML sequence diagrams are used to represent or model the flow of messages, events and actions between the objects or components of a system. Time is represented in the vertical direction showing the sequence of interactions of the header elements, which are displayed horizontally at the top of the diagram.

Sequence Diagrams are used primarily to design, document and validate the architecture, interfaces and logic of the system by describing the sequence of actions that need to be performed to complete a task or scenario. UML sequence diagrams are useful design tools because they provide a dynamic view of the system behavior which can be difficult to extract from static diagrams or specifications.

Although UML sequence diagrams are typically used to describe object-oriented software systems, they are also extremely useful as system engineering tools to design system architectures, in business process engineering as process flow diagrams, as message sequence charts and call flows for telecom/wireless system design, and for protocol stack design and analysis.

Include 1 link to a useful page about Sequence Diagrams

http://sourceforge.net/projects/staruml/forums

Include the link to download StarUML

http://staruml.sourceforge.net/en/download.php