MYSQL 1Z0-874 問題集

質問 1：
What will be the effect of executing the following statement?
REVOKE ALL PRIVILEGES FROM 'web'@'localhost'
A. The account 'web'@'localhost' will no longer be usable for login, but since there is no ON clause, privileges are retained for re-enabling the account at a later time.
B. The account 'web'@'localhost' will lose all privileges except for USAGE
C. The account 'web'@'localhost' will have all privileges removed, and the account deleted from the server.
D. Nothing. A REVOKE statment without an ON clause is invalid
正解：B

質問 2：
When performing diagnostic functions on a server should excessive start and stop messages be looked for in the error log, and why?
A. No, because they will not provide any information as to what is wrong.
B. No, start and stop messages are of no relevance to diagnostics.
C. Yes, because there is a bug in mysqld that can cause multiple start and stop messages to be inserted in the log.
D. Yes, because they can indicate that there is something causing the server to restart unexpectedly and not due to normal startup and shutdown.
正解：D

質問 3：
Which of the following should be done to enable secure logging of events which may be needed for recovery operations and to track down security incidents? (Choose three)
A. Set the --encrypt-logs option
B. Enable the binary log
C. Enable the slow log
D. Enable the general log
E. Set permissions on log files so they are only readable by the user owning the mysql process
正解：B,D,E

質問 4：
The stored function year_to_date is created by the 'root'@'localhost' account as follows:
CREATE FUNCTION year_to_date ()
RETURNS DECIMAL(10,2)
SQL SECURITY DEFINER
BEGIN ... END;
Within the routine body, a number of calculations are made on data in the financials table and the calculated value is returned. The only account which can access the financials table is 'root'@'localhost'.
If a client connects with the account
'joe'@'localhost' and calls the year_to_date function, what will happen?
A. The function will always execute as if it was 'root'@'localhost' that invoked it since SQL SECURITY DEFINER has been specified.
B. The function will not execute, as 'joe'@'localhost' does not have access to the financials table
C. The function will not execute as SQL SECURITY DEFINER has been specified. It would execute if instead SQL SECURITY INVOKER had been specified
D. If the account 'joe'@'localhost' has the EXECUTE privilege on year_to_date, the function will complete successfully
正解：D

質問 5：
Is it a good idea to do periodic table rebuilds for InnoDB tables? Why?
A. No, because the indexes have to be rebuilt.
B. Yes, because the table may become fragmented after many INSERTs and DELETEs.
C. No, because there is a risk for data corruption.
D. Yes, because it flushes the logs and frees memory.
正解：B

質問 6：
Which of the following best describes why InnoDB tables should always have primary keys and why they should be short?
A. Because InnoDB uses primary keys to locate tables, and shorter keys make quicker lookups.
B. Because InnoDB uses primary keys to locate table rows, and shorter keys make quicker lookups.
C. Because InnoDB stores pointers in a log to all the primary keys and shorter keys make this log smaller.
正解：B

質問 7：
Given the following MyISAM table structure:
mysql> desc city;
+-------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------+------+-----+---------+----------------+
| ID | int(11) | | PRI | NULL | auto_increment |
| Name | char(35) | | | | |
| CountryCode | char(3) | | | | |
| District | char(20) | | | | |
| Population | int(11) | | MUL | 0 | |
+-------------+----------+------+-----+---------+----------------+
And the following SQL statement: SELECT Population FROM city WHERE Population = 10000
ORDER BY Population LIMIT 5; which of the following statements best describes how MySQL
optimizer executes the query?
A. The optimizer will never read data from disk, since MySQL caches both data and index in the key buffer.
B. The optimizer uses the primary key column ID to read the index values, then uses the index on Population to filter the results. The optimizer will always choose to use a unique index first, then use a secondary index if available.
C. The optimizer uses the index on the Population column to search and filter the WHERE clause. A temporary table is used to perform a filesort on the results, and then only 5 records are returned to the client.
D. The optimizer uses the index on the Population column to search, filter and sort the Population column, and returns 5 records to the client. The optimizer does not need to read the data rows, and can return values from the index only because only those columns where specified in the SELECT statement.
E. The optimizer uses the index on the Population column to search, filter and sort the Population column, then returns 5 records to the client. The optimizer does not need to read the data rows, and can return values from the index only, because the index contains just integer values that form a leftmost prefix for the key.
正解：D

質問 8：
Consider the following: mysql> EXPLAIN SELECT * FROM City WHERE CountryCode = 'USA' *************************** 1. row *************************** id: 1 select_type: SIMPLE table: City type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 4079
Extra: Using where
What does it mean that the possible_keys column value is NULL?
A. No index is considered available for this query.
B. You are not making use of any available indexes in your query.
C. No index exists for the table you are querying.
正解：A

質問 9：
Which of the following statements are true of how access control is based?
A. It is based off of an access control list stored inside the .frm files of each table.
B. It is based off of an access control table in the mysql database.
C. It is based off of grant tables in the mysql database.
D. it is based off of an access control list stored in the data directory.
正解：C