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7 Cards in this Set
- Front
- Back
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Name 2 problems with flat file databases and why they're problems! |
•There is data duplication which makes input errors more likely • Not all duplicated data will be updated during an update |
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What is the main advantage of relational databases? |
• Data only needs to be entered once, therefore, data integrity is maintained |
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How are tables within relational databases linked to each other? |
• Primary Keys • Foreign Keys |
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What data is held in the 'Calculated' data type in a database. |
• It holds a formula that performs a calculation on the contents for fields in the same table • The value stored is the result of the calculation |
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Name 3 types of validation, found in a database, and their function. |
• Range Check - Limits the range of acceptable numbers • Length Check - Limits the maximum amount of text that can be entered • Presence Check - Makes a field 'required'. Data must be entered in that field • Format - This can make the user enter, e.g, a date in the form DD/MM/YYYY. |
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Name all of the keys and their function. |
• Primary Key - Unique identifier of records • Foreign Key - A Primary key in a different table • Compound Key - A combination of primary keys that uniquely identify a record |
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Describe what the field attribute 'Format' does. |
• Sets out how the field data is to be displayed • It does not affect how data is stored within a database E.g- Sets the no. of decimal points of a real - Sets how a time will be displayed |
