True False solution 2009 2010

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2009

True False solution

1. A composite PRIMARY KEY is created by using the table-level definition.
2. A foreign key value must match an existing value in the parent table or be NULL.
3. A single column can have multiple CHECK constraints which refer to the column in its definition. There is no limit to the number of CHECK constraints which you can define on a column. CHECK constraints can be defined at the column level or table level.
4. The GROUP BY column does not have to be in the SELECT clause. You can use the group function in the ORDER BY clause.
5. You can remove privileges granted to other users by using the REVOKE statement.
6. Null values are displayed last for ascending sequences and first for descending sequences.
7. ….
8. You can present logical subsets or combinations of data by creating views of tables. A logical table based on a table or another view. A view contains no data of its own but is through which data from tables can be viewed or changed. The tables on which a view called base tables. The view is stored as a SELECT statement in the data dictionary.
9. A PRIMARY KEY constraint creates a primary key for the table. Only one primary key can be created for each table. The PRIMARY KEY constraint is a column or set of columns that uniquely identifies each row in a table. This constraint enforces uniqueness of the column or column combination and ensures that no column that is part of the primary key can contain a null value.
10. NVL Conversions for Various Data Types

Data Type	Conversion Example
NUMBER	NVL(number_column,9)
DATE	NVL(date_column, ’01-JAN-95’)
CHAR or VARCHAR2	NVL(character_column, ’Unavailable’)

11. ….
12. The default display of queries is all rows, including duplicate rows.
13. You can remove existing rows from a table by using the DELETE statement.
14. The NOT NULL constraint can be specified only at the column level, not at the table level.
15. The WHERE clause follows the FROM clause.
16. UNIQUE constraints allow the input of nulls unless you also define NOT NULL constraints for the same columns.
17. …..
18. VIEW Can be dropped without removing the underlying data
19. ….
20. Performing DML Operations on a View. You can perform DML operations on data through a view if those operations follow certain rules. You can remove a row from a view unless it contains any of the following:
• • Group functions
• • A GROUP BY clause
• • The DISTINCT keyword
• • The pseudocolumn ROWNUM keyword
21. …….
22. Use the HAVING clause to restrict groups:
• Rows are grouped.
• The group function is applied.
• Groups matching the HAVING clause are
• displayed.
23. You can sort by a column that is not in the SELECT list.
24. ……………….

Default Ordering of Data

The default sort order is ascending:

• Numeric values are displayed with the lowest values first—for example, 1–999.

• Date values are displayed with the earliest value first—for example, 01-JAN-92 before

01-JAN-95.

• Character values are displayed in alphabetical order—for example, A first and Z last.

• Null values are displayed last for ascending sequences and first for descending sequences.

Reversing the Default Order

To reverse the order in which rows are displayed, specify the DESC keyword after the column name

the ORDER BY clause. The slide example sorts the result by the most recently hired employee.

2010

True False solution

1. A DML statement is executed when you:

–       Add new rows to a table

–       Modify existing rows in a table

–       Remove existing rows from a table

2. ……………………
3. A foreign key value must match an existing value in the parent table or be NULL.

Foreign keys are based on data values and are purely logical, not physical, pointers.

4. A privilege granted on a synonym is converted to a privilege on the base table referenced by the synonym.
5. ….
6. When Does a Transaction Start and End?

A transaction begins when the first DML statement is encountered and ends when one of the

following occurs:

• • A COMMIT or ROLLBACK statement is issued
• • A DDL statement, such as CREATE, is issued
• • A DCL statement is issued
• • The user exits iSQL*Plus
• • A machine fails or the system crashes

After one transaction ends, the next executable SQL statement automatically starts the next

transaction.

A DDL statement or a DCL statement is automatically committed and therefore implicitly ends a

transaction.

7. All columns in the SELECT list that are not group functions are included in the GROUP BY clause.
8. ……
9. Any column or expression in the SELECT list that is not an aggregate function must be in the GROUP BY clause.
10. Columns without the NOT NULL constraint can contain null values by default.
11. COUNT(*) returns the number of rows in a table that satisfy the criteria of the SELECT statement, including duplicate rows and rows containing null values in any of the columns.
12. What is an Index?

An index:

• • Is a schema object
• • Is used by the Oracle server to speed up the
• retrieval of rows by using a pointer
• • Can reduce disk I/O by using a rapid path access
• method to locate data quickly
• • Is independent of the table it indexes
• • Is used and maintained automatically by the
• Oracle server
12. You can decrease the width of a column only if the column contains only null values or if the table has no rows.
13. Only one primary key can be created for each table.
14. To drop an index, you must be the owner of the index or have the DROP ANY INDEX privilege.
15. Single-row functions can be nested to any depth.
16. Table names and column names must begin with a letter and be 1–30 characters long.
17. …………….
18. NVL Function

Converts a null to an actual value.

• • Data types that can be used are date, character,
• and number.
• • Data types must match:

–       NVL(commission_pct,0)

–       NVL(hire_date,’01-JAN-97’)

–       NVL(job_id,’No Job Yet’)

20. Values specified with the BETWEEN condition are inclusive. You must specify the lower limit first.
21. A view is a logical table based on a table or another view. A view contains no data of its own but is like a window through which data from tables can be viewed or changed. The tables on which a view is based are called base tables. The view is stored as a SELECT statement in the data dictionary.
22. Performing DML Operations on a View You can perform DML operations on data through a view if those operations follow certain rules. You can remove a row from a view unless it contains any of the following:
• • Group functions
• • A GROUP BY clause
• • The DISTINCT keyword
• • The pseudocolumn ROWNUM keyword
23. You can use the group function in the ORDER BY clause.
24. When you drop an integrity constraint, that constraint is no longer enforced by the Oracle server and is no longer available in the data dictionary.