2025 WGU D427/ D427 WGU Exam Data Management
Applications New Version with Questions and 100% Correct
Answers
An operator is a symbol that computes a value from one or more other values, called
___________: ----------- Correct Answer ------------ operands
A relational rule that requires foreign key values are either fully NULL or match some primary
key value is known as what? ----------- Correct Answer ------------ Referential Integrity
*In a relational database, foreign keys must obey referential integrity at all times.
Referential integrity can be violated in four ways: ----------- Correct Answer ------------ 1. A
primary key is updated.
2. A foreign key is updated.
3. A row containing a primary key is deleted.
4. A row containing a foreign key is inserted.
Databases automatically correct referential integrity violations with any of four actions, specified
as SQL constraints: ----------- Correct Answer ------------ RESTRICT rejects an insert, update, or
delete that violates referential integrity.
SET NULL sets invalid foreign keys to NULL.
SET DEFAULT sets invalid foreign keys to the foreign key default value.
CASCADE propagates primary key changes to foreign keys.
RESTRICT, SET NULL, and SET DEFAULT apply to primary key update and delete, and
foreign key insert and update. ----------- Correct Answer ------------ CASCADE applies to
primary key update and delete only.
What do the parentheses denote? ----------- Correct Answer ------------- The column values for
two individual rows
What happens in an UPDATE statement if the WHERE clause is omitted? ----------- Correct
Answer ------------- Every row in the table is updated.
Which action deletes all rows from a table? ----------- Correct Answer ------------- Omitting the
WHERE clause from a DELETE statement
What is the purpose of using a SELECT statement? ----------- Correct Answer ------------- To
retrieve data
Which SQL statement retrieves all of the columns from the Owners table? ----------- Correct
,Answer ------------- SELECT * FROM Owners;
Which SQL statement tallies the number of different cities in which record companies have been
founded? ----------- Correct Answer ------------- SELECT COUNT(DISTINCT city) FROM
recordcompany;
Which task does ORDER BY perform by default? ----------- Correct Answer ------------- Sorting
rows in ascending order
Actions are specified in the optional ON UPDATE and ON DELETE clauses of the FOREIGN
KEY constraint. How does this look syntatically? ----------- Correct Answer ------------ ON
UPDATE and ON DELETE are followed by either RESTRICT, SET NULL, SET DEFAULT, or
CASCADE.
A ____________ is a rule that governs allowable values in a database. ----------- Correct Answer
------------ constraint
*Constraints are based on relational and business rules, and implemented with special keywords
in a CREATE TABLE statement.
_______________ operators compute logical values TRUE or FALSE. ----------- Correct Answer
------------ Comparison
Operands may be numeric, character, and other data types.
A _________ operator has one operand. ----------- Correct Answer ------------ unary
A __________ operator has two operands. ----------- Correct Answer ------------ binary
Most operators are binary.
The logical operator "NOT" is _______. The arithmetic operator - is either unary or binary. ------
----- Correct Answer ------------ unary
An ______________ is a string of operators, operands, and parentheses that evaluates to a single
value. ----------- Correct Answer ------------ expression
*Operands may be column names or fixed values. The value of an expression may be any data
type.
The order of operator evaluation may affect the value of an expression. Operators in an
expression are evaluated in the order of ___________ _____________ ----------- Correct Answer
------------ operator precedence
*Operators of the same precedence are evaluated from left to right.
**Regardless of operator precedence, expressions enclosed in parentheses are evaluated before
any operators outside the parentheses are applied.
, The ________ clause limits the number of rows returned by a SELECT statement. -----------
Correct Answer ------------ LIMIT
A ___________ is an expression that evaluates to a logical value. ----------- Correct Answer ------
------ condition
A SELECT statement has an optional ___________ clause that specifies a condition for selecting
rows. A row is selected when the condition is TRUE for the row values. A row is omitted when
the condition is either FALSE or NULL. ----------- Correct Answer ------------ WHERE
*When a SELECT statement has no WHERE clause, all rows are selected.
The _______ ________ constraint prevents a column from having a NULL value. -----------
Correct Answer ------------ NOT NULL
*Statements that insert NULL, or update a value to NULL, are automatically rejected.
**NOT NULL follows the column name and data type in a CREATE TABLE statement.
(T/F) Since comparison operators return NULL when either operand is NULL, comparison
operators cannot be used to select NULL values. ----------- Correct Answer ------------ True
*Ex: SELECT * FROM Employee WHERE Salary = NULL; never returns any rows, because
the WHERE clause is always NULL.
What two operators are used to select rows with NULL values? ----------- Correct Answer --------
---- the IS NULL and IS NOT NULL operators must be used to select NULL values.
*Value IS NULL returns TRUE when the value is NULL. Value IS NOT NULL returns TRUE
when the value is not NULL.
In traditional mathematical logic, expressions are always TRUE or FALSE. When NULL is
present, however, a logical expression may be either TRUE, FALSE, or NULL. The NULL
value indicates what? ----------- Correct Answer ------------ That the value of a logical expression
is uncertain.
In query results false is represented as ___ and True is represented as ___. ----------- Correct
Answer ------------ False is represented at 0
True is represented as 1
The INSERT statement does what? ----------- Correct Answer ------------ adds rows to a table
What are the two clauses that are in an INSERT statment? ----------- Correct Answer ------------
INSERT INTO clause names the table and columns where data is to be added. The keyword
INTO is optional.
The VALUES clause specifies the column values to be added.
A default value may be specified for a column. Meaning, the column is assigned the default
value, rather than NULL, when omitted from an INSERT statement. Where is default specified
in the syntax? ----------- Correct Answer ------------ The optional DEFAULT keyword and default
value follow the column name and data type in a CREATE TABLE statement.
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