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Question
Which of the following is not true about subtype entities?A) Subtypes may be exclusive.
B) The supertype and subtypes will have the same identifier.
C) Subtypes are used to avoid a situation in which some attributes are required to be null.
D) All subtypes of a supertype must have the same attributes.
Answer
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Related questions
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Suppose you have created a data model for an airline based on a variety of forms, reports, user interviews, data sources, etc. Your client comes forward with a new desired report that includes passenger weights and a relationship between passengers and employees, neither of which is in your E-R diagram. You should ________.
A) create a new, separate E-R diagram with just the new information
B) add the relationship and the weight attribute to the existing data model
C) add the relationship but not the weight attribute
D) add the weight attribute but not the relationship
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In a 1:N relationship, the term parent refers to the N side of the relationship.
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Relationships are classified by their cardinality.
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In today's E-R models, attributes of relationships are still used.
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Entities can be associated with one another in relationships.
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In E-R modeling, entities within an entity class may have different attributes.
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To check for null values in a column in a table, use the SQL phrase ________.
A) IS
B) IS NOT
C) IS NULL
D) COUNT(NULL)
Q:
When a table is created using existing data from multiple sources, you are likely to find that the different sources code data in slightly different ways. This is an example of ________.
A) the multivalued, multicolumn problem
B) the inconsistent values problem
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Q:
A classic example of unneeded normalization is when we are dealing with ________.
A) ZIP codes
B) sales orders and line items
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Q:
The SQL keyword TOP ________.
A) limits the number of columns retrieved from a table
B) limits the number of rows retrieved from a table
C) limits the number of tables retrieved from a database
D) A and C
Q:
During the second step of assessing table structure, you are trying to determine ________.
A) relationships
B) candidate keys
C) updatability
D) efficiency
Q:
The first step in assessing table structure includes ________.
A) counting rows
B) examining columns
C) examining data values
D) Both A and B are correct
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A null value in a column may indicate that there is an appropriate value for that attribute, but it is unknown.
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An inconsistent values problem is created when different users have coded the same data entries differently.
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Q:
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