023,我星期日要考试了，谁知道答案的话，一定要告诉我

显示全部楼层 · 2005-10-30 17:05:33

question one :
two tables have a parent-child relationship that will be enforced by a primary key constraint and foreign key constaint.you would like the flexibility to insert rows in the child table before inserting rows in the parent table.what must you create to enforce the primary key constraint with a unique index ?
a.both constraints deferrable
b.the foreign key constraints deferrable and the primary key constraint not deferrable.
c.both constraints not deferrable, and use the set contraint command todefer checking of the foreign key constraint as needed
d.both constraints not deferrable,and use the alter session command to defer checking of the foreign key constraint as needed.
e.the foreign key constraints deferrable,and use the alter table command to defer checking of the foreign key constraint as needed.
the anwer isb,but idon't knowwhy?
can you tell me the anwer is right or wrong?

question two:
what are two characteristics of the control file ?(choose two)
a.it has a fixed size.
b.it should the multiplexed.
c.it can be edited by the dba.
d.it is required to start the instance.
e.it is required to open the database.
i think the answer is a and b .
can you tell me i am right or wrong ?
which type of index should be created tospread the distribution of index
updates across the index tree?
a.b-tree indexes
b.bitmap indexes
c.reverse-key indexes
d.function-based indexes
do you knowthe answer?

which category of data dictionary views does not have an owner column?
a.my_
b.dba_
c.all_
d.uses_
do you knowthe answer?

which two commands can cause a database event trigger to fire ?(choose two )
a.drop user
b.alter view
c.call procedure
d.create database
doyou know the answer?

千问 · 2005-10-30 17:05:33

最初由 shq1125 发布
[B]question one :
two tables have a parent-child relationship that will be enforced by a primary key constraint and foreign key constaint.you would like the flexibility to insert rows in the child table before inserting rows in the parent table.what must you create to enforce the primary key constraint with a unique index ?
a.both constraints deferrable
b.the foreign key constraints deferrable and the primary key constraint not deferrable.
c.both constraints not deferrable, and use the set contraint command todefer checking of the foreign key constraint as needed
d.both constraints not deferrable,and use the alter session command to defer checking of the foreign key constraint as needed.
e.the foreign key constraints deferrable,and use the alter table command to defer checking of the foreign key constraint as needed.
the anwer isb,but idon't knowwhy?
can you tell me the anwer is right or wrong?

question two:
what are two characteristics of the control file ?(choose two)
a.it has a fixed size.
b.it should the multiplexed.
c.it can be edited by the dba.
d.it is required to start the instance.
e.it is required to open the database.
i think the answer is a and b .
can you tell me i am right or wrong ? b.e
which type of index should be created tospread the distribution of index
updates across the index tree?
a.b-tree indexes
b.bitmap indexes
c.reverse-key indexes
d.function-based indexes
do you knowthe answer? c

which category of data dictionary views does not have an owner column?
a.my_
b.dba_
c.all_
d.uses_
do you knowthe answer? d

which two commands can cause a database event trigger to fire ?(choose two )
a.drop user
b.alter view
c.call procedure
d.create database
doyou know the answer? a.b
[/B]
不一定正确

千问 · 2005-10-30 17:05:33

b
be
c
d
ab

千问 · 2005-10-30 17:05:33

which two commands can cause a database event trigger to fire ?(choose two )
a.drop user
b.alter view
c.call procedure
d.create database
ANSWER: A B
BECAUSE:
Triggering event
– Instance startup or shutdown
– A specific error message or any error message
– User logon or logoff
– A DML statement on a specific table or view
– A DDL statement on any schema
1. Data Definition Language(DDL) Statements
--Create,alter,and drop schema objects
--Grant and revoke privileges and roles
--Analyze information on a table,index,or cluster
--Establish auditing options
--Add comments to the data dictionary
Oracle implicitly commit the current transaction before and after every DDL statement
2. Data Manipulation Language(DML) Statements
--Call
--Delete
--Explain plan
--Insert
--Lock Table
--Select
--Update
DML statements query and manipulate data in existing schema objects.
DML statements do not implicitly commit the current transaction.

千问 · 2005-10-30 17:05:33

which category of data dictionary views does not have an owner column?
a.my_
b.dba_
c.all_
d.uses_
ANSWERD
BECAUSE:
Views with the USER Prefix
The views most likely to be of interest to typical database users are those with the
USER prefix. These views:
? Refer to the user’s own private environment in the database
? Generally refer to objects owned by the current user
? Have columns identical to the other views, except that the column OWNER is
implied to be the current user
? Return a subset of the information in the ALL_ views
? Can have abbreviated PUBLIC synonyms for convenience

千问 · 2005-10-30 17:05:33

pengxiaohui
版主
the control file size is dertemined by the MAX clauses you provide
when you create the database--maxlogfiles,maxlogmembers,maxloghistory,maxdatafiles and maxinstances
therfore ,when you add or rename a file in the databasemthe control file size does not change.
what the meaning ofthese?is it tell me the control file size does not change?

千问 · 2005-10-30 17:05:33

which type of index should be created to spread the distribution of index
updates across the index tree?
a.b-tree indexes
b.bitmap indexes
c.reverse-key indexes
d.function-based indexes
ANSWERC
BECAUSE:
Classification of Indexes
? Logical
– Single column or concatenated
– Unique or nonunique
– Function-based
A function-based index is created when using functions or expressions that involve
one or more columns in the table being indexed. A function-based index precomputes
the value of the function or expression and stores it in the index. Function-based
indexes can be created as either a B-tree or a bitmap index.
? Physical
– Partitioned or nonpartitioned
– B-tree
At the top of the index is the root, which contains entries that point to the next level in
the index. At the next level are branch blocks, which in turn point to blocks at the next
level in the index. At the lowest level are the leaf nodes, which contain the index
entries that point to rows in the table. The leaf blocks are doubly linked to facilitate
scanning the index in an ascending as well as descending order of key values.
– Normal or reverse key
In contrast to a regular B-tree index, a reverse key index reverses the bytes of each
column indexed (except the ROWID) while keeping the column order. When inserting
records on an ascending key, such as a system-generated employee number, I/O
bottlenecks can occur on the index because all index updates occur at the same place
in the index tree. Reverse key indexes spread the distribution of index updates across
the index tree by reversing the data value of the index key.
– Bitmap
A bitmap index is also organized as a B-tree, but the leaf node stores a bitmap for each
key value instead of a list of ROWIDS. Each bit in the bitmap corresponds to a
possible ROWID, and if the bit is set, it means that the row with the corresponding
ROWID contains the key value.
Bitmap indexes are more advantageous than B-tree indexes in certain situations:
? When a table has millions of rows and the key columns have low cardinality—that
is, there are very few distinct values for the column. For example, bitmap indexes
may be preferable to B-tree indexes for the gender and marital status columns of a
table containing passport records.
? When queries often use a combination of multiple WHERE conditions involving
the OR operator.
? When there is read-only or low update activity on the key columns.

千问 · 2005-10-30 17:05:33

最初由 shq1125 发布
[B]pengxiaohui
版主
the control file size is dertemined by the MAX clauses you provide
when you create the database--maxlogfiles,maxlogmembers,maxloghistory,maxdatafiles and maxinstances
therfore ,when you add or rename a file in the databasemthe control file size does not change.
what the meaning ofthese?is it tell me the control file size does not change? [/B]
这意味着, 如果你要更改control file 的size, 那么必须重新create database

千问 · 2005-10-30 17:05:33

最初由 shq1125 发布
[B]
which two commands can cause a database event trigger to fire ?(choose two )
a.drop user
b.alter view
c.call procedure
d.create database
doyou know the answer?
[/B]
类似的一道题目是这样的, 可以帮助你加深理解:
Which two events can cause a database event trigger to fire? (Choose two.)

A. creating a user
*

B. creating a database

C. executing a procedure

D. altering an instance parameter

E. adding a constraint to an existing table
*

千问 · 2005-10-30 17:05:33

question two:
what are two characteristics of the control file ?(choose two)
a.it has a fixed size.
b.it should the multiplexed.
c.it can be edited by the dba.
d.it is required to start the instance.
e.it is required to open the database.
ANSWERB E
BECAUSE:
You might need to re-create the control file to change one or more of the database limit
parameters, which could increase or decrease the size of the control file.
The size of the control file is influenced by the following keywords in the CREATE
DATABASE or CREATE CONTROLFILE commands:
? MAXLOGFILES
? MAXLOGMEMBERS
? MAXLOGHISTORY
? MAXDATAFILES
? MAXINSTANCES
To safeguard against a single point of failure of the control file, it is strongly
recommended that you multiplex the control file, storing each copy on a different
physical disk.
The information in the control file can be modified only by the Oracle server;
no DBA or end user can edit the control file.
Starting the Instance Usually you would start an instance without mounting a
database only during database creation or the re-creation of control files.
Starting an instance includes the following tasks:
? Reading the parameter file init sid.ora
? Allocating the SGA
? Starting the background processes
? Opening the ALERT file and the trace files
The database must be named with the DB_NAME parameter either in the
init SID.ora file or in the STARTUP command.
Mounting the Database To perform specific maintenance operations, you start an
instance and mount a database but do not open the database.
For example, the database must be mounted but not open during the following tasks:
? Renaming data files
? Enabling and disabling redo log archiving options
? Performing full database recovery
Mounting a database includes the following tasks:
? Associating a database with a previously started instance
? Locating and opening the control files specified in the parameter file
? Reading the control files to obtain the names and status of the data files and redo
log files (However, no checks are performed to verify the existence of the data files
and online redo log files at this time.)
Opening the Database Normal database operation means that an instance is started
and the database is mounted and open; this allows any valid user to connect to the
database and perform typical data access operations.
Opening the database includes the following tasks:
? Opening the online data files
? Opening the online redo log files
If any of the data files or online redo log files are not present when you attempt to open
the database, the Oracle server returns an error.
During this final stage, the Oracle server verifies that all the data files and online redo
log files can be opened and checks the consistency of the database. If necessary, the
System Monitor background process (SMON) initiates instance recovery.