WGU D426/427
1. What is a subquery: A query within another SQL query.
2. What is an alias in SQL: A temporary name assigned to a column or table, created with the AS keyword.
3. What is a materialized view: A view for which data is stored at all times and must be refreshed when the base table
changes.
4. What does the WITH CHECK OPTION clause do: Ensures that inserts and updates in a view satisfy the
view's WHERE clause.
5. What is an entity in entity-relationship modeling: A person, place, product, concept, or activity.
6. What is a relationship in entity-relationship modeling: A statement about two entities.
7. What is an attribute in entity-relationship modeling: A descriptive property of an entity.
8. What is a reflexive relationship: A relationship that relates an entity to itself.
9. What is an entity-relationship diagram (ER diagram): A schematic picture of entities, relationships, and
attributes, where entities are drawn as rectangles.
10.What is an entity type: A set of things, such as all employees in a company.
11.What is a relationship type: A set of related things, such as employee-man- ages-department pairs.
12.What is an attribute type: A set of values, such as all employee salaries.
13.What is an entity instance: An individual thing, such as the employee Sam Snead.
14.What is a relationship instance: A specific statement about entity instances, such as "Maria Rodriguez manages
Sales."
15.What is an attribute instance: An individual value, such as a salary of $35,000.
16.What is cardinality in entity-relationship modeling: The maxima and minima of relationships and attributes.
17.What is a subtype entity: A subset of another entity type, called the supertype entity.
18.What is a supertype entity: An entity that has one or more subtype entities, such as "vehicle" with subtypes
like "car" and "truck."
19.What is an IsA relationship: The identifying relationship between a supertype and its subtypes.
20.What is a partition in entity-relationship modeling: A group of mutually exclusive subtype entities
within a supertype entity.
21.What is crow's foot notation: A convention for depicting cardinality in ER diagrams, using symbols like circles,
short lines, and three short lines (a crow's foot).
22.What is an intangible entity: An entity documented in the data model but not tracked with data in the database.
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, WGU D426/427
23.What are the characteristics of a primary key: A primary key should be stable, simple, and meaningless.
24.What is an artificial key: A single-column primary key created by the database designer when no suitable primary
key exists.
25.What is functional dependence: The dependence of one column on another.
26.What is redundancy in databases: The repetition of related values in a table.
27.What is a candidate key: A simple or composite column that is unique and minimal, with all columns
necessary for uniqueness.
28.What is a non-key column: A column that is not contained in a candidate key.
29.What is third normal form: A table is in third normal form if, whenever a non-key column A depends on column
B, then B is unique.
30.What is Boyce-Codd normal form: A stricter form of third normal form where column B must be unique
regardless of whether it is a candidate key.
31.What is a trivial dependency: When the columns of A are a subset of the columns of B, A always depends
on B.
32.What is normalization: The process of eliminating redundancy by decompos- ing a table into two or more tables
in higher normal form.
33.What is denormalization: The intentional introduction of redundancy by merg- ing tables.
34.What is a heap table: A table where no order is imposed on rows, optimizing insert operations.
35.What is a sorted table: A table where rows are physically ordered by a specified sort column.
36.What is a hash table: A table where rows are assigned to buckets, optimizing search and retrieval.
37.What is a table cluster: A storage structure that interleaves rows of two or more tables in the same storage area.
38.What is a table scan: A database operation that reads table blocks directly without using an index.
39.What is an index scan: A database operation that reads index blocks sequen- tially to locate the needed table
blocks.
40.What is a hit ratio (filter factor: selectivity), The percentage of table rows selected by a query.
41. What is a binary search: A search method where the database repeatedly splits the index in two until the
search value is found.
42.What is a dense index: An index that contains an entry for every table row.
43.What is a sparse index: An index that contains an entry for every table block.
44.What is a hash index: An index where entries are assigned to buckets.
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1. What is a subquery: A query within another SQL query.
2. What is an alias in SQL: A temporary name assigned to a column or table, created with the AS keyword.
3. What is a materialized view: A view for which data is stored at all times and must be refreshed when the base table
changes.
4. What does the WITH CHECK OPTION clause do: Ensures that inserts and updates in a view satisfy the
view's WHERE clause.
5. What is an entity in entity-relationship modeling: A person, place, product, concept, or activity.
6. What is a relationship in entity-relationship modeling: A statement about two entities.
7. What is an attribute in entity-relationship modeling: A descriptive property of an entity.
8. What is a reflexive relationship: A relationship that relates an entity to itself.
9. What is an entity-relationship diagram (ER diagram): A schematic picture of entities, relationships, and
attributes, where entities are drawn as rectangles.
10.What is an entity type: A set of things, such as all employees in a company.
11.What is a relationship type: A set of related things, such as employee-man- ages-department pairs.
12.What is an attribute type: A set of values, such as all employee salaries.
13.What is an entity instance: An individual thing, such as the employee Sam Snead.
14.What is a relationship instance: A specific statement about entity instances, such as "Maria Rodriguez manages
Sales."
15.What is an attribute instance: An individual value, such as a salary of $35,000.
16.What is cardinality in entity-relationship modeling: The maxima and minima of relationships and attributes.
17.What is a subtype entity: A subset of another entity type, called the supertype entity.
18.What is a supertype entity: An entity that has one or more subtype entities, such as "vehicle" with subtypes
like "car" and "truck."
19.What is an IsA relationship: The identifying relationship between a supertype and its subtypes.
20.What is a partition in entity-relationship modeling: A group of mutually exclusive subtype entities
within a supertype entity.
21.What is crow's foot notation: A convention for depicting cardinality in ER diagrams, using symbols like circles,
short lines, and three short lines (a crow's foot).
22.What is an intangible entity: An entity documented in the data model but not tracked with data in the database.
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5
, WGU D426/427
23.What are the characteristics of a primary key: A primary key should be stable, simple, and meaningless.
24.What is an artificial key: A single-column primary key created by the database designer when no suitable primary
key exists.
25.What is functional dependence: The dependence of one column on another.
26.What is redundancy in databases: The repetition of related values in a table.
27.What is a candidate key: A simple or composite column that is unique and minimal, with all columns
necessary for uniqueness.
28.What is a non-key column: A column that is not contained in a candidate key.
29.What is third normal form: A table is in third normal form if, whenever a non-key column A depends on column
B, then B is unique.
30.What is Boyce-Codd normal form: A stricter form of third normal form where column B must be unique
regardless of whether it is a candidate key.
31.What is a trivial dependency: When the columns of A are a subset of the columns of B, A always depends
on B.
32.What is normalization: The process of eliminating redundancy by decompos- ing a table into two or more tables
in higher normal form.
33.What is denormalization: The intentional introduction of redundancy by merg- ing tables.
34.What is a heap table: A table where no order is imposed on rows, optimizing insert operations.
35.What is a sorted table: A table where rows are physically ordered by a specified sort column.
36.What is a hash table: A table where rows are assigned to buckets, optimizing search and retrieval.
37.What is a table cluster: A storage structure that interleaves rows of two or more tables in the same storage area.
38.What is a table scan: A database operation that reads table blocks directly without using an index.
39.What is an index scan: A database operation that reads index blocks sequen- tially to locate the needed table
blocks.
40.What is a hit ratio (filter factor: selectivity), The percentage of table rows selected by a query.
41. What is a binary search: A search method where the database repeatedly splits the index in two until the
search value is found.
42.What is a dense index: An index that contains an entry for every table row.
43.What is a sparse index: An index that contains an entry for every table block.
44.What is a hash index: An index where entries are assigned to buckets.
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