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What is a database?
A database is an organised collection of data
What advantages do electronic databases have over manual databases?
- Electronic databases (library catalogue system) have many advantages over manual databases (phonebooks) such as:
- Store large quantities of information with storage devices
- Search and store data accurately
- Organise information in many ways
- Information can be presented in different ways i.e. tables, forms, reports
What is a flat file?
A flat file database organises data into a single table which isn’t appropriate for large amounts of data
What is relational database?
For huge amounts of data there is relational databases, where data is organised using a series of related tables
How is a database created?
- Using database programs such a MS Access
- Variety of database programs such as database management system (DBMS) and file managers
What is a file manager?
File managers allow users to work with one file at a time to create a flat file database
What is DataBase Management System (DBMS)?
A DBMS is a software package that allows the user to enter maintain and provide access to a collection of files, creating a relational database
What are components of a database?
Files, fields, records and characters
Describe the components of a database.
- A file is a block of related data stored on a storage device. For example, an student database is stored as a file
- A record is a collection of facts about one specific entry in a database. All the information about one student is known as a record
- A field is a specific piece of data in a record. Fields for students would be the student’s last name, first name, date of birth. A field is typically known as a category
- A character is the smallest the unit of data such as letters, numbers and symbols
What is a data dictionary? What does it contain?
- It is known as a detailed description of each field
- It contains information about the characteristics of each item entered in the database, such as the field names, data types, field sizes and field descriptions
What is a field name?
Field name is the name of a field. They should be short, clear and avoid punctuation
What is a data type? List and describe them?
- Data type is the kind of data entered in the field. These can be:
- Text -used for text or numbers that don’t require calculations
- Memo -used for lengthy text and numbers such as descriptions
- Number -used for numeric data that require calculations
- Currency -used for monetary values
- Auto number -used to automatically create a unique number for each record
- Yes/No- used for data that has opposite values
- OLE object -used for data in other programs such as spreadsheets
- Hyperlink -used for hyperlinks
- Date/time -used for date and time
What is a field size?
Field size is the number of characters allowed in a field
What is a description?
Description specifies contents of the field
What is a table?
A table displays data using fields and records
How do you change a table?
There are several ways to change the screen layout for table such as changing the width of columns, hiding a column or altering row height
What does the table limit?
Tables allow more than one record but limits the fields to what will fit across the screen. Tables are convenient when working with several records
What is a form?
A form displays data for every field of a single record. The layout is changeable
How is data entered into a table?
Using a form.
How is data in a table retrieved?
Using a query.
What does a well designed form have?
- Well designed forms provide information explaining the required data and any data entry rules that apply to fields
- Drop-down lists are used to ensure the correct data is used
- Fonts need to be carefully chosen
What should you do when collecting data?
- Decide what to collect– Will it be a file, record or field
- Identify the source of data– Where can the data be found
- How will the data be gathered– Will it be through surveys, questioners, interviews etc
- Gather the data– Collect and enter it into the DBMS
What are primary and secondary sources?
- Primary sources is when data is collected first hand, this is more reliable however it is time-consuming and costly
- Secondary sources is when data is collected or created by someone else. This is easy, cheap and frees up time however it can be unreliable so be sure to get data from a variety of sources and check the copyright issues on it
When is a magnetic disk used?
Magnetic disk storage is used when immediate access to data is required, it uses direct access
When is a magnetic tape used?
Magnetic tape is used as a backup medium for databases, it can store large quantities of data inexpensively however it uses sequential access
How are backups used? Explain the processes?
Backups (another copy of data that could be used to rebuild the system) are also used. It may involve three generations of backups files known as the grandfather-father-son system, which is commonly used for magnetic tapes.
What is file fragmentation? How does it occur?
Database storage and retrieval may occur many times each day and results in file fragmentation. It occurs when a file is broken and stored in separate segments on a disk. Bad fragmentation= slow access
What does data validation do?
Checks the entry of data and is used to detect any missing or mistyped data
How are data validation errors reduced?
Data validation errors have been reduced by using check boxes and drop-down lists
What do data validation rules perform?
Data validation rules are also entered to perform a range check, list check, type check and check digit on data
What does data verification do?
Checks whether the entered data is accurate and is performed by a person
What is bad about data verification
- The accuracy of data is difficult since some errors can go undetected for some time
- Data can also become corrupted or damaged after entry, thus using backups is vital
What is editing in terms of data? How is data edited?
- It is the process of changing data
- Data is inserted into a field by placing the cursor in the desired location
- Data is deleted by a field by either highlighting or placing your cursor there and clicking delete
- Data is moved with the cut, copy and paste commands
How can you modify the structure of data?
By changing the data dictionary
What is sorting?
- It is arranging data in a particular order
- Can be performed in ascending or descending order
- When numbers in a text field is sorted, it is according the order of characters, not the size, for instance, ‘25’ will come before ‘9’ because 2 is smaller than 9To sort records , the user chooses a field and then selects ascending or descending order
What is a two level sort?
There is what you call a two-level sort, were data is sorted on more than one field, for instance, if you want to sort ‘Last name’ by alphabetical order, the first name moves with it
What is searching? How is this carried out?
- The process of locating data/information
- For small databases, you can use the find and search commands
- For large databases you use a query– a search of a database for records that meet a criteria
How is a query created?
Queries are constructed using an operator. It is created by selecting the ‘query commands’ and selecting the fields the user wants displayed
What is a QBE (Query By Example)?
Query By Example (QBE) requires data to be entered against a fields. For example, if you were looking for a person with a last name of Fisher you would type =‘Fisher’ in the ‘Last name’ field and leave the remaining fields blank. The DBMS would then search the database and select all the records that have Fisher as a ‘Last name’
What is an operator? What are the two types?
- Represent the actions to be performed by the query
- Logical and relational
What are logical operators?
Logical operators (and, or not) combine two or more single queries
What are relational operators?
Relational operators (=, <>, <, >, <=, >=) are symbols that indicate the relationship between two expressions
What are 'and' 'or' operators?
- The ‘and’ operator requires both the first and second query to be true, so it only retrieves records that appear in both queries
- The ‘or’ operator requires either the first or second query to be true, so it retrieves all the records from both queries
What are wild card characters?
- Represent one or more unknown characters
- Two wildcard key characters are the * which represents any number of characters and a ? Which represents only one character
What are mathematical calculations?
- a predefined calculation—uses functions such as sum, average, count, minimum and maximum
- custom calculation—the user writes a formula to perform a calculation
What is a report? What is its purpose?
- Formatted and organised presentation of data
- Purpose of the report will determine its content, format and style
What does a report contain?
- Reports usually have:
- The report header appears once at the beginning of a report.
- The page header displays information such as a title, column headings
- A page header appears after the report header on the first page of the report.
- Most of the information will be displayed in the detail section
- The page footer displays information such as the date, page number
- The report footer displays items such as report totals, appears in the last page
What are some design principles?
- Forms and report should be simple and layout should be the same throughout to promote reading gravity (reading info from top to bottom, left to right)
- Different size headings to reflect importance
- To improve readability in a form or report, use a lot of white space
- Colour scheme should be carefully chosen
What are macros?
Set of actions that user creates to automate common task. It used to perform operations such as opening a form/report, usually repetitive task to reduce keyboard errors.
How is a macro made?
It is created by entering the actions to be completed by the macro, naming it then carrying out by clicking the ‘run’ command
What is integration?
It is the process of merging data from other sources
What is importing?
Importing is copying/ taking data producing by another program
What is exporting?
Exporting is when you send data to another program
What is embedding?
- Occurs if the copy is not connected to the source. The copy is fixed and does not change is the source is change
- Used when information does not have to be updated automatically, e.g. Entering a graphic of an apple into a form about apples
What is linking?
- Occurs if the copy is connected to the source
- Useful when your documents require current information for other sources, e.g. A report based on changing statistics
What is cut, copy, paste?
Used to import and export data
How do you import with cut, copy, paste?
To import, you open the application and file, move to the correct location and click ‘paste’ for embedding’
How do you export with cut, copy, paste?
To export, you select the data to be transferred, use ‘cut’ to remove the data or ‘copy’ to duplicate it then paste to another program
What is mail merge?
- Combines a document written on a word processor with data from another source, such as a database. For example, an organisation create a database of names and addressed and use a word processor to generate personalised letters, then merge them
- Saves time and makes each document look individually written
Name the three steps involved in mail merge?
Setting up a data source, setting up a merge document and merging the document.
What is 'set up a data source' in terms on mail merge?
Set up a data source– Data source contains the data to be merge into the other document
What is 'set up a merged document" in terms on mail merge?
Set up the merged document- Word processors and publishing programs are often used to create the merged document. After the document is written, select the Mail Merge command. A data source is then selected and the cursor positioned where the data is to be inserted. A merged field is chosen from the data source. More than one merged field can be inserted if required.
What is "merge the documents" in terms of mail merge?
Merge the documents– A merge command will replace the selected fields with data. Each record from the data source produces an individual version of the merged document