QCE Digital Solutions Unit 3: Redundancy, referential integrity and table joins
Students remove redundancy and anomalies by splitting tables, model and enforce relationships between them, and combine tables with joins.
One content description from the full QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems journey. All 19 modules below are in that journey too, with the same content — add just these to a class, or the whole strand.
Modules (19)
1
The repeated-data problem in one big table
2
Update, insertion and deletion anomalies
3
Reducing redundancy by splitting a table
4
Foreign key and table relationships
5
One-to-many relationships between tables
6
One-to-one and many-to-many relationships
7
Entity relationship diagram: entities and relationship lines
8
Crow's foot notation for one and many
9
Drawing an ERD from a scenario
10
Referential integrity
11
FOREIGN KEY ... REFERENCES in CREATE TABLE
12
Why a query over two tables needs a join
13
Writing the ON condition: foreign key equals primary key
14
Table-qualified field names in a join
15
Table aliases in a join
16
A join with WHERE and ORDER BY
17
Joining three tables
18
A join that forgets the ON condition
19
Answering a question with a multi-table query
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