This document discusses database design concepts including primary keys, foreign keys, relationships between tables, normalization, and different types of queries. It covers one-to-one, one-to-many, and many-to-many relationships and how to implement them. It also discusses referential integrity, data validation, indexes, anomalies that can occur without normalization, and different types of joins and queries.
3. Have more than one table where tables are
related to each other
One to one
One to many
Many to many
A combination of fields may be used for the
table‟s primary key
4. Each table contains data about a specific
subject (customers, loans)
Each table on the „one‟ side has a primary
key
Primary key of the “one” table is a foreign
key in the many table
5. Twotables are related, but can have many
records in each table in common
One student can attend many courses; one
course can be attended by many students
Implement a many to many relationship by
creating a pair of one to many relationships
with a third table
Third table is often referred to as a “join” or
“junction” table
6. A foreign key points to a record in another
table
Foreign key “looks like” the related primary
key
Same number of fields
Data types for each field must match
Field names don‟t matter
7. Makessure that the records in related tables
are consistent
Must have a customer in the customer table for
an order assigned to that customer
Avoids “orphans”
Cannotdelete a record or change the
primary key in the one table when associated
records are in the many table, unless have
cascade delete and cascade update enabled
8. Data constraints: What is “good” data?
Valid type of data
Valid values for the data
Many can be enforced through the design of the
Access tables and relationships
9. Validation rule: Condition that the
corresponding field must satisfy
Validation text: Displayed if the condition of
validation rule is not satisfied
Table Properties validation rule: Required
when a constraint requires a comparison of
the contents of two or more fields in the
same table
10. Maintains a sorted list of the current values
of a field or fields
Items in the list point to the records that
have the identified value
Created automatically for primary keys
11. Normalization is a process
Goals:
Reduce space required to store data by
eliminating duplicate data in database
Reduce inconsistent data in database by storing
data only once
Reduce chance anomalies
12. Deletion anomaly
User deletes data from database
Unintentionally deletes only occurrence of data
in database
Update anomaly
Due to redundant data in database
User fails to update some records or updates
records erroneously
Insertion anomaly
User cannot add data to database unless
preceded by entry of other data
13. Dependency: Column value depends on value
in a different column
Functional dependency: values explicitly one to
one
Partial dependency: Column value dependent on
only part of primary/candidate key
14. Determinant: Field or collection of fields
whose value determines value in another
field
Inverse of dependency
Department is a determinant
15. Retrieve data from other tables or queries
Field names appear in the Field row of the
grid
Criteria row of grid
Limits the displayed rows to those that meet a
specified condition
Contains any statement that evaluates to True or
False
16. Inner join
Default join type
Includes rows only when the fields being
compared contain matching values
Outer join
Includes all rows from one table and data from
second table where there is a match
17. Use when selecting records from one table,
but need to limit the records returned by a
value in another table
Use the „In‟ comparison
Sub-query can return only a single field
Sub-query must run before the main query
Use parentheses to control order of execution
18. Select queries that aggregate values
The Group By item in the Total list box tells
Access to aggregate the other fields per each
unique value within the Group By field
A field that‟s part of the aggregate uses
Having instead of Where
19. Delete queries: Remove rows from a table
Make-table queries: Query results are stored
in a new table
Append queries: Query results of the are
appended (added) to an existing Access table
Update queries: Change field values in
existing rows in a table
20. Parameter queries use placeholder to
substitute for the constant values placed in
the query grid
Allow changes to criteria “on the fly” when
the query is run