1.3.1 Databases Flashcards

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1
Q

What is a database?

A

A structured store of data. Usually consists of tables, fields, and records.

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2
Q

What is a flat-file database, and the issues they face?

A
  • A database where all data is stored in one table
  • Difficult to change the format of the data
  • Space is wasted through redundant data
  • Data is harder to update as it could be in multiple places
  • Data might become inconsistent for example the amount of an item in stock might be reduced in one record but not in other records.
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3
Q

Define a relational database and the benefits of using them.

A

Multiple related tables

Simpler to change the format of data

Saves space by reducing data duplication

Maintains data consistency/integrity

Improved security as able to control access to data

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4
Q

Define a primary key

A

A field that has a unique value to act as a unique identifier for every record in that table. e.g. UserID in a table of users.

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5
Q

Define a foreign key

A

A field that links to a (primary) key in a second table.

Provides a link between tables

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6
Q

Define and give an example of a secondary key.

A

Not unique but are likely to be the fields that users are likely to want to search by. Surname in a user table.

Indexed allowing for faster searching.

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7
Q

Define indexing and its associated pros and cons.

A

The index gives the position of each record according to its primary key.

Advantage: Searches of indexed fields can be performed more quickly.

Disadvantage: The index has to be rebuilt on edit and takes up extra space in the database.

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8
Q

What three types of database relationships exist, and which one is prohibited?

A

1:1 – One to One
1:M – One to Many
M:M – Many to many (prohibited)

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9
Q

What would a resolved M:M relationship diagram look like?

A

M:M - These need to be resolved using a middle table with many coming out of each side.

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10
Q

Give some examples of how data can be captured.

A

Online Form

Optical Character Recognition (OCR)

Optical Mark Recognition (OMR)

Sensors

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11
Q

Give some examples of sensors and what they may be used for.

A

Altimeter: Measures height from sea level

Accelerometer: Measure forces – When it moves.

Gyroscope: Used to measure rotation.

Thermistor: To read the temperature

GPS: To determine geographical location

Magnetometer: To determine direction.

Heart rate sensor: Detects electrical activity in the heart

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12
Q

Give some examples of the methods used to exchange data.

A

CSV: A format with values separated by commas

JSON: Uses human-readable text to transmit data objects consisting of attribute-value pairs

XML: A mark-up language that uses tags to denote data.

API: A prewritten set of subroutines that provide access to a company’s data. Used by programmers to transfer data between computer systems.

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13
Q

What is the SQL to select all data from a table?

A

SELECT column_name(s)
FROM table_name

or

SELECT * FROM table_name

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14
Q

What is the SQL to delete data from a table?

A

DELETE FROM table_name
WHERE some_column=some_value

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15
Q

What is the SQL to insert data into a table?

A

INSERT INTO table_name
VALUES (value1, value2…)

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16
Q

What is the SQL to remove a table?

A

DROP TABLE table_name

17
Q

What is the SQL to remove a column?

A

ALTER TABLE table_name
DROP COLUMN column_name

18
Q

What is the SQL to join two tables together?

A

SELECT column_name(s)
FROM table_name1
JOIN table_name2ON table_name1.column_name = table_name2.column_name

19
Q

What is the SQL to select all fields from a table where the data in a column ends with ‘th’?

A

SELECT * FROM table_name WHERE column_name LIKE ‘%th’

20
Q

What is the SQL to update a value in a table?

A

UPDATE table_name
SET column1=value, column2=value
WHERE some_column=some_value