marți, 24 noiembrie 2009

Quiz: Introduction to Relational Database Concepts


1. One or more columns in a primary key can be null. True or False?
True
False (*)
2. Foreign keys cannot be null when:
It is part of a primary key. (*)
It refers to another table.
It contains three or more columns.
3. A foreign key always refers to a primary key in the same table. True or False?
True
False (*)
4. The explanation below defines which constraint type:
A primary key must be unique, and no part of the primary key can be null.
Entity integrity. (*)
Referential integrity.
Column integrity.
User-defined integrity.
5. The explanation below defines which constraint type:
A column must contain only values consistent with the defined data format of the column.
Entity integrity.
Referential integrity.
Column integrity. (*)
User-defined integrity.
6. Column integrity refers to:
Columns always having values.
Columns always containing positive numbers.
Columns always containing values consistent with the defined data format. (*)
Columns always containing text data less than 255 characters.
7. The explanation below is an example of what constraint type:
The value in the dept_no column of the EMPLOYEES table must match a value in the dept_no column in the DEPARTMENTS table.
Entity integrity.
Referential integrity. (*)
Column integrity.
User-defined integrity.
8. Identify all of the correct statements that complete this sentence: A primary key is: (Choose Three)
A single column that uniquely identifies each row in a table. (*)
A set of columns that uniquely identifies each row in a table. (*)
A set of columns and keys in a single table that uniquely identifies each row in a single table. (*)
Only one column that cannot be null.
9. The explanation below is an example of what constraint type:
If the value in the balance column of the ACCOUNTS table is below 100, we must send a letter to the account owner which will require extra programming to enforce.
Entity integrity.
Referential integrity.
Column integrity.
User-defined integrity. (*)
10. A table does not have to have a primary key. True or False?
True (*)
False

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