QCE Digital Solutions Unit 2 Definitions Worksheet: Data and Programming Techniques (Modules 186–228)
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Date:
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Key terms
Write what each term means, in your own words.
1
Availability
2
stream
3
filter
4
map
5
aggregate
6
ALTER TABLE
7
CREATE VIEW
8
secondary key
9
NULL
Answer Key
QCE Digital Solutions Unit 2 · Modules 186–228 · Student wording will vary for definitions
1Availability — Authorised users can reach data and systems when they need them. Hardware failure and attacks can threaten it, so backups and protection keep a system running.
2stream — A sequence of structured records that arrives or is read one at a time, such as sensor readings, file lines or API results, and is processed as it flows.
3filter — Keep only the records in a stream that meet a condition and discard the rest, usually with an if inside a loop that adds matches to a result list.
4map — map() applies a function to every record in a stream and gives back changed records, such as converting a type, trimming and changing the case of text, or computing a derived field.
5aggregate — To aggregate is to combine many records into one summary value, such as a running total, a count of matching records, or an average worked out after the loop.
6ALTER TABLE — An SQL command that changes the structure of an existing table, such as adding a column with ADD, removing one with DROP COLUMN, or adding a FOREIGN KEY, without deleting the table.
7CREATE VIEW — Saves a SELECT query as a named virtual table. It shows chosen columns and rows, can hide others, and stores no copy of the data, so you query it like a table.
8secondary key — A non-primary field used to search or sort records, such as surname. Unlike a primary key, its values need not be unique, and it is often indexed to make searches faster.
9NULL — A field with no value at all. It is not zero and not an empty string. Test for it with IS NULL, never = NULL. A primary key can never be NULL.