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Session Objectives # 20

Session Objectives # 20 . Key Words. Key Words. Field. Record. Data Type. Primary Key. Query. Validation. Database Schema. Database File.

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Session Objectives # 20

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  1. Session Objectives# 20

  2. Key Words Key Words Field Record Data Type Primary Key Query Validation

  3. Database Schema Database File This is the main file that holds the entire database. It’s usually saved on a hard drive or network server but can be saved on a portable storage device. A table is a collection of data about a specific topic, i.e table of student names and addresses There can be many tables in a single database. When these tables are linked together it is known as a relational database. Table Record A group of fields which are related in some way, i.e a student record could be: Surname, Forename, Date of Birth, Tutor Group etc. Field Individual data items with their own data type are known as fields. An example is a Date of Birth field (NB its data type will be Date) Data Type Data types are the properties of each field. Each field only has one data type – this aids storage and searching facilities. Value A value is each individual data entry, occupying one cell, i.e, for the student record example, it could be just a students’ Surname.

  4. Data Types Test Mr Smith 38 High Street, Weston – Super – Mare Somerset BS23 6AR (0117) 9236666 JohnSmith@yahoo.co.uk 1/11/05 Text 1 Number 2 3 Text Alpha Numeric – Text or Memo 4 5 Text 6 Hyperlink 7 Date/Time

  5. Logical Operators < <= = > >= <> Less than • Less than or equal to • Equal to • More than • More than or equal to • Not equal to

  6. Use of Logical Operators Write the following statements using logical operators Less than £200 Greater than £300 Equal to or more than £500 Less than or equal to £150 Greater than £225 Everything that is not equal to £250

  7. Database Interrogation This is the technical term for searching a database or querying. TASK: Complete the Customer Enquires tasks on the travel agent database. EXTENSION: Customer Enquiries 2

  8. Data Validation This means to only allow sensible or valid data into the system at the point of entry. There are many methods which can be used to reduce the chance of data entry errors. Can you think of any?? • Format check or Input Mask– e.g. 2 letters then 2 numbers – PR15 would be valid. • Presence check– checking that the field contains data. • Range check – data is between certain numbers or letters, e.g. A–E. • Lookup check – only values from a set list can be entered, e.g. M or F. • Size check – checking data is more or less than a minimum or maximum number of characters.

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