Databases - Tools and techniques. Tables.

Databases - Tools and techniques. Tables.

1. Table Characteristics

   • Rows and columns
   • Columns = Fields
   • Rows = Records
   • Field types
     • Alphabetic
       • Text
       • Memo
     • Numeric
       • Numbers
       • Currency
       • Dates
       • Times
     • Boolean/logical
       • Yes/No
       • True/False
     • Web
       • Hyperlink
     • Lookup wizards
     • Field size
       • Byte
       • Integer
       • Long integer
       • Single
       • Double
       • Decimal
     • Field Formats
       • Fixed
       • Decimal places
     • Default values

2. Validation

   • To check for errors
   • Applies to a range
   • Correct format
     • Postcode
       • Input mask
   • Correct field size
   • Correct data type
   • Types
     • Check digit
       • When the last one or two digits are used to check the other digits in a code are correct
       • Bar code readers in supermarkets use check digits
     • Format check
       • Check that data is in the right format
       • A National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number
     • Length check
       • Makes sure the data isn't too long or short
       • A password which needs to be six letters long
     • Lookup table
       • Looks up acceptable values in a table
       • There's only seven possible days in the week
     • Presence check
       • Checks that data has been Entered into a field
       • In most databases an important field can't be left blank
     • Range check
       • Checks that a value is within the specified range
       • Number of hours worked must be less than 50 and more than 0
     • Spell check
       • Looks up words in a dictionary
       • When word processing

3. Records

   • Add
     • Manually
     • External source
       • Spreadsheets
   • Edit
   • Delete

4. Indexing

   • Primary key
   • Foreign key

5. Relationships

   • One to many
   • Many to many
   • One to one