Managing Databases with Oracle Questions and Answers

Q: The left-leaning slash tells Oracle to execute whatever statement is in the buffer.

Correct answer: FalseIt is the forward slash that executes the buffer, not a backslash, and typing a backslash achieves nothing. The distinction matters in practice because the slash is how a statement is re-run after being corrected, and how a PL/SQL block is submitted - a semicolon cannot end such a block, since its body is full of semicolons already.

Q: What type of failure occurs when Oracle fails due to an operating system or computer hardware failure?

Correct answer: Instance FailureInstance failure is the loss of the Oracle instance itself - the memory structures and background processes - through an operating system crash, a hardware fault or a power loss. The datafiles are undamaged, so recovery is automatic on the next startup: Oracle rolls forward the redo log and rolls back uncommitted transactions. Media failure, by contrast, means the files themselves are damaged and needs a restore.

Q: Which of the following is NOT an Oracle-supported trigger?

Correct answer: DURINGOracle triggers fire BEFORE or AFTER the triggering statement, or INSTEAD OF it, the last being used on views that are not otherwise updatable. There is no DURING option, and there could not usefully be one, since the statement is atomic from the trigger’s point of view.

Q: The semicolon terminates a SQL statement (and executes it).

Correct answer: TrueA semicolon at the end of a line terminates the statement and submits it for execution in one action, which is the ordinary way of running a single SQL statement. The alternative is a slash on a line of its own, which executes whatever is already in the buffer and is needed for PL/SQL blocks.

Q: The default extension for SQL*Plus is .sql.

Correct answer: TrueSQL*Plus assumes the extension .sql when a file name is given without one, so a script saved as build.sql is run simply as @build. The convention is worth following, since a file with any other extension has to be named in full every time it is used.

Q: Which SQL phrase is not supported by Oracle?

Correct answer: ON UPDATE CASCADEOracle supports ON DELETE CASCADE but not ON UPDATE CASCADE, so a change to a parent key value cannot be propagated automatically to the children; it must be done with a trigger or, better, avoided by using a surrogate key that never changes. The two sequence commands are both supported.

Q: What is the type of Oracle backup in which all uncommitted changes have been removed from the datafiles?

Correct answer: Consistent backupA consistent backup is taken with the database cleanly shut down, so every datafile is at the same system change number and no uncommitted change remains in it. It can be restored without applying redo. An inconsistent backup is taken with the database open and does require redo to be applied before it can be used.

Q: Oracle directly supports the definition of surrogate keys.

Correct answer: FalseOracle has no declaration that makes a column a surrogate key. The usual construction is a sequence to generate the values together with a trigger that assigns the next value on insert, or in later versions an identity column, but neither is a direct definition of a surrogate key in the sense the statement claims.

Q: After a table has been created, its structure can be modified using the SQL command:

Correct answer: ALTER TABLE [ TableName ].ALTER TABLE is the standard command for changing an existing table - adding or dropping a column, changing a datatype, adding or removing a constraint. UPDATE changes data rather than structure, and the other two are not SQL commands at all.

41.

The left-leaning slash tells Oracle to execute whatever statement is in the buffer.

A.True
B.False

Answer: B

Correct answer: False

It is the forward slash that executes the buffer, not a backslash, and typing a backslash achieves nothing. The distinction matters in practice because the slash is how a statement is re-run after being corrected, and how a PL/SQL block is submitted - a semicolon cannot end such a block, since its body is full of semicolons already.

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42.

What type of failure occurs when Oracle fails due to an operating system or computer hardware failure?

A.Application failure
B.Instance Failure
C.Media Failure
D.Rollback failure

Answer: B

Correct answer: Instance Failure

Instance failure is the loss of the Oracle instance itself - the memory structures and background processes - through an operating system crash, a hardware fault or a power loss. The datafiles are undamaged, so recovery is automatic on the next startup: Oracle rolls forward the redo log and rolls back uncommitted transactions. Media failure, by contrast, means the files themselves are damaged and needs a restore.

Discuss in Forum

43.

Which of the following is NOT an Oracle-supported trigger?

A.BEFORE
B.DURING
C.AFTER
D.INSTEAD OF

Answer: B

Correct answer: DURING

Oracle triggers fire BEFORE or AFTER the triggering statement, or INSTEAD OF it, the last being used on views that are not otherwise updatable. There is no DURING option, and there could not usefully be one, since the statement is atomic from the trigger’s point of view.

Discuss in Forum

44.

The semicolon terminates a SQL statement (and executes it).

A.True
B.False

Answer: A

Correct answer: True

A semicolon at the end of a line terminates the statement and submits it for execution in one action, which is the ordinary way of running a single SQL statement. The alternative is a slash on a line of its own, which executes whatever is already in the buffer and is needed for PL/SQL blocks.

Discuss in Forum

45.

The default extension for SQL*Plus is .sql.

A.True
B.False

Answer: A

Correct answer: True

SQL*Plus assumes the extension .sql when a file name is given without one, so a script saved as build.sql is run simply as @build. The convention is worth following, since a file with any other extension has to be named in full every time it is used.

Discuss in Forum

46.

Which SQL phrase is not supported by Oracle?

A.ON DELETE CASCADE
B.ON UPDATE CASCADE
C.CREATE SEQUENCE [SequenceName]
D.DROP SEQUENCE [SequenceName]

Answer: B

Correct answer: ON UPDATE CASCADE

Oracle supports ON DELETE CASCADE but not ON UPDATE CASCADE, so a change to a parent key value cannot be propagated automatically to the children; it must be done with a trigger or, better, avoided by using a surrogate key that never changes. The two sequence commands are both supported.

Discuss in Forum

47.

What is the type of Oracle backup in which all uncommitted changes have been removed from the datafiles?

A.Full backup
B.Consistent backup
C.Inconsistent backup
D.Differential backup

Answer: B

Correct answer: Consistent backup

A consistent backup is taken with the database cleanly shut down, so every datafile is at the same system change number and no uncommitted change remains in it. It can be restored without applying redo. An inconsistent backup is taken with the database open and does require redo to be applied before it can be used.

Discuss in Forum

48.

Oracle directly supports the definition of surrogate keys.

A.True
B.False

Answer: B

Correct answer: False

Oracle has no declaration that makes a column a surrogate key. The usual construction is a sequence to generate the values together with a trigger that assigns the next value on insert, or in later versions an identity column, but neither is a direct definition of a surrogate key in the sense the statement claims.

Discuss in Forum

49.

After a table has been created, its structure can be modified using the SQL command:

A.UPDATE TABLE [TableName].
B.MODIFY TABLE [TableName].
C.ALTER TABLE [TableName].
D.CHANGE TABLE [TableName].

Answer: C

Correct answer: ALTER TABLE [ TableName ].

ALTER TABLE is the standard command for changing an existing table - adding or dropping a column, changing a datatype, adding or removing a constraint. UPDATE changes data rather than structure, and the other two are not SQL commands at all.

Discuss in Forum

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