AQA GCSE Computer Science - SQL and Relational Databases

What is a Database?

A structured way to store data so that it can be retrieved using queries.

What is a Table?

A collection of related data entries that consists of columns and rows.

What is a Record?

A single entry in a table, which contains data for each field.

What is a Field?

A specific piece of data within a record, defined by a field name.

What is a Primary key?

A field that stores unique data for each record in a table.

Describe the Integer datatype?

A whole number data type.

Describe the Real datatype?

A number data type with a decimal component.

Describe the Float datatype?

A number data type that can represent fractional values.

Describe the Decimal datatype?

A number data type with a fixed number of decimal places.

Describe the Date datatype?

A data type used to store dates.

Describe the Time datatype?

A data type used to store time.

Describe the DateTime datatype?

A data type used to store both date and time.

Describe the Char datatype?

A fixed length string data type, up to 8,000 characters.

Describe the Varchar datatype?

A variable length string data type, up to 8,000 characters.

Describe the Text datatype?

A variable length string data type, up to 2 GB of data.

What is a Flat file database?

A database that stores a single table of data inside a single text file.

What is Redundant data?

Data that is repeated in each record, leading to inconsistencies and increased storage use.

What is a Relational database?

Databases that solve issues of redundancy and data inconsistency found in flat file databases.

SQL

Structured Query Language

AND

A logical operator used to combine multiple conditions in a SQL query.

OR

A logical operator used to include records that meet at least one of multiple conditions in a SQL query.

LIKE

A SQL operator used to search for a specified pattern in a column.

SELECT

A SQL statement used to specify the fields to be displayed in a query.

FROM

A SQL statement used to specify the table name from which to retrieve data.

WHERE

A SQL clause used to specify the search criteria for records.

ORDER BY

A SQL clause used to sort the result set in ascending (ASC) or descending (DESC) order.

ASC

Specifies ascending order in an ORDER BY clause.

DESC

Specifies descending order in an ORDER BY clause.

wildcard

A character used in SQL queries, such as *, to represent all columns.

INSERT INTO

A SQL statement used to add new records to a table.

UPDATE... SET

A SQL statement used to modify existing records in a table.

DELETE FROM

A SQL statement used to remove records from a table.

WHERE clause

A clause in SQL that specifies conditions for filtering records.

Operators in the WHERE clause

Symbols used to compare values, including =, !=, >, <, >=, <=, AND, OR, NOT.

BETWEEN

An operator that specifies an inclusive range in SQL queries.

Wildcard %

A character in SQL that substitutes for zero, one, or more characters in a LIKE string.

ORDER BY keyword

A clause in SQL that sorts the result set in ascending or descending order.

UPDATE statement

An SQL command used to modify existing records in a table.

DELETE statement

An SQL command used to remove records from a table.

JOIN

A SQL operation that combines rows from two or more tables based on a related column.

SELECT *

A SQL command that selects all columns from a table.

SELECT * FROM Animal

An SQL command that selects all fields for all animals from the Animal table.

UPDATE Animals SET Height_m

An SQL command that modifies the height of a specific animal in the Animals table.

DELETE FROM Animals

An SQL command that removes a specific animal record from the Animals table.

WHERE Town = 'Ipswich'

A condition in an SQL query that filters results to only include members from Ipswich.

WHERE Breed = 'Labrador' AND Colour = 'Brown'

A condition in an SQL query that filters results to include only brown Labradors.

WHERE Owners.DogsID = Dogs.DogsID

A condition in an SQL query that links owners to their dogs based on a common identifier. Used as a JOIN.