Definitions - 1.3 Exchanging Data

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  • Created by: osymonds
  • Created on: 09-11-17 14:07
Lossy Compression
All non-essential data is permanently removed
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Lossless Compression
Looks for repeated patterns to reduce the data held. No data is lost. Run-length or Dictionary compression.
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Flat File Database
One table database of a plain text file with one record per line
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Primary Key
Unique Identifier for a record
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Secondary Key
A unique identifier that is not the Primary key
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Foreign Key
Connects tables to each other
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ACID
Atomicity, Consistency, Isolation, Durability
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Atomicity
A transaction is processed in its entirety or not at all.
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Consistency
No validation rules are broken.
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Isolation
concurrent execution of transactions leads to the same result as if transactions were processed one after the other
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Durability
This ensures that once a transaction has been committed, it will remain so, even in the event of a power cut.
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Dictionary Compression
Look for repeated items or patters stored in a dictionary matrix with a set value and replace the repeated part with the value each time it comes up.
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Run-Length Compression
Look at repeated singular characters of colors. Store as a value and the number of times it turns up.
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Alter Table - SQL
ALTER TABLE tblProduct (/n) ADD QtyInStock INTEGER
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Delete a Column - SQL
ALTER TABLE tblProduct (/n) DROP QtyInStock
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Change the Data Type of a Column - SQL
ALTER TABLE tblProduct (/n) MODIFY COLUMN Description VARCHAR (30) NOT NULL
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Insert new record - SQL
ProductID CHAR(4) NOT NULL, PRIMARY KEY Description (/n) VARCHAR(20) NOT NULL Price (/n) CURRENCY
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Insert new value - SQL
INSERT INTO Product (ProductID, Description, Price) (/n) VALUES (“A345”, “Pink Rabbit”, 7.50)
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Update a record - SQL
UPDATE Product (/n) SET Description = “Blue Rabbit”, Price = 8.25 (/n) WHERE ProductID = “A345”
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Delete an record - SQL
DELETE FROM Product (/n) WHERE ProductID = “A345”
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Other cards in this set

Card 2

Front

Looks for repeated patterns to reduce the data held. No data is lost. Run-length or Dictionary compression.

Back

Lossless Compression

Card 3

Front

One table database of a plain text file with one record per line

Back

Preview of the back of card 3

Card 4

Front

Unique Identifier for a record

Back

Preview of the back of card 4

Card 5

Front

A unique identifier that is not the Primary key

Back

Preview of the back of card 5
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