MYSQL 1Z0-874 問題集

質問 1：
Consider the following: ALTER TABLE City ROW_FORMAT = FIXED What would be the effect of this statement?
A. Nothing as this is not a valid statement.
B. The columns in the table City are changed from VARCHAR to CHAR.
C. The table City is changed to a fixed row format.
正解：C

質問 2：
Does the ordering of tables shown in an EXPLAIN output have any significance? Why?
A. No, the order is determined by the order in which tables are specified in the statement being EXPLAINed.
B. Yes, it sorts by the most optimized to the least optimized.
C. Yes, it determines the table from which data will read first.
D. No, it sorts them alphabetically.
正解：C

質問 3：
Consider the following EXPLAIN of a simple Join:
mysql> EXPLAIN SELECT CountryList.Name, CityList.Name, CityList.Population
-> FROM CountryList JOIN CityList ON CountryList.Code = CityList.Country
-> WHERE CityList.Population > 8000000 *************************** 1. row *************************** id: 1 select_type: SIMPLE table: CountryList type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 239 Extra: *************************** 2. row *************************** id: 1 select_type: SIMPLE table: CityList type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 4079 Extra:
Using where How many rows need to be examined to perform the join?
A. 2159, the average of both numbers
B. 4079, the number of rows in the second table
C. 4318, the sum of both numbers
D. 239, the number of rows in the first table
E. 974881, the product of both numbers
正解：E

質問 4：
Which of the following are true regarding the usage of the IDENTIFIED BY clause in the GRANT statement used to create a new user account? (Choose two)
A. The IDENTIFIED BY clause specifies the password to be used with the account
B. The IDENTIFIED BY clause is always mandatory
C. There is no IDENTIFIED BY clause for the GRANT statement
D. The IDENTIFIED BY clause specifies an alternate user name for the account
E. The IDENTIFIED BY clause is always optional
F. The IDENTIFIED BY clause may be mandatory depending on the current SQL mode
正解：A,F

質問 5：
Which of the following statements are true of compressed tables?
A. They can be uncompressed but some data corruption may occur.
B. They can be uncompressed.
C. They can not be uncompressed.
正解：B

質問 6：
Which of the following best describes why one should use VARCHAR rather than CHAR in InnoDB? (Choose two)
A. Generally, there will be less disk I/O during processing.
B. VARCHAR columns provide better transaction support.
C. The average amount of space used will be less.
D. The optimizer always performs better with VARCHAR columns over CHAR columns.
正解：A,C

質問 7：
Which of the following best describes the purpose of the join buffer, and when should you increase the size of it? (Choose three)
A. The value should be increased if the client has the tendency to perform complex joins.
B. The join buffer is used to process sorts when complex joins are being performed.
C. The join buffer is global and can only be changed by restarting the server.
D. The value should be increased if the client performs a lot of SELECT operations.
E. The join buffer is set per-connection.
F. The join buffer is used to process joins.
正解：A,E,F

質問 8：
Which of the following are important network factors for remote MySQL clients? (Choose two)
A. Firewalls.
B. The type of routers used.
C. Latency.
D. Throughput speed.
正解：C,D

質問 9：
Connection strings in FEDERATED tables are stored...
A. In variables.
B. In a .fed file corresponding to the table.
C. Within the table definition.
D. They are not stored, but must be re-specified at server restart.
正解：C