ACARA Digital Technologies Years 9–10 Definitions Worksheet: Entities, Relationships and Queries (Modules 459–475)
Name:
Date:
Class:
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Key terms
Write what each term means, in your own words.
1
WHERE lastName LIKE 'S%'
2
BETWEEN low AND high
3
JOIN
4
ON orders.customer_id = customers.customer_id
5
table.field
6
FROM students s
7
JOIN ... ON ... WHERE ... ORDER BY
8
JOIN subjects ON results.subjectId = subjects.subjectId
9
Cartesian product
10
multi-table query
Answer Key
ACARA Digital Technologies Years 9–10 · Modules 459–475 · Student wording will vary for definitions
1WHERE lastName LIKE 'S%' — LIKE matches text by pattern in a WHERE clause. % stands for any run of characters and _ for exactly one, so 'S%' finds values starting with S and '%son' finds values ending in son.
2BETWEEN low AND high — Tests if a value is inside a range, including both limits. Its partner IN (a, b, c) checks a value against a list, replacing repeated OR. NOT IN excludes the list.
3JOIN — A join matches each foreign key value in one table to the primary key value in another, so rows from both tables show together. Rows with no match are left out.
4ON orders.customer_id = customers.customer_id — The join condition: it matches the foreign key in one table to the primary key in the other. The = sign compares the two values to find matching rows. It does not assign a value.
5table.field — Names the table a field comes from, like students.name. Needed in a join when both tables share a field name, or SQL gives an ambiguous column error.
6FROM students s — Gives the students table the short name s after FROM, so the rest of the query can write s.firstName instead of students.firstName.
7JOIN ... ON ... WHERE ... ORDER BY — After JOIN ... ON links two tables, WHERE filters the joined rows and ORDER BY sorts them. Clause order: SELECT, FROM, JOIN ON, WHERE, ORDER BY.
8JOIN subjects ON results.subjectId = subjects.subjectId — A second JOIN line chained after the first to reach a third table. It follows a foreign key in the junction table to the primary key of the next table.
9Cartesian product — A join with no ON condition pairs every row of one table with every row of the other, so 3 customers and 4 orders give 12 rows, most of them wrong.
10multi-table query — A query that gets fields from more than one table: find which tables hold them, JOIN them on matching keys, then add WHERE and ORDER BY to match the question.