What isolation level prevents dirty reads, nonrepeatable reads, and phantoms、

试卷相关题目

• 1What is the act of exchanging one lock an application holds on a resource for a more restrictive lock on the same resource known as、

  A.Lock escalation

  B.Lock substitution

  C.Lock switch/exchange

  D.Lock conversion/promotion

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• 2When is an INTENT EXCLUSIVE (IX) lock required、

  A.When a transaction intends to read or change data.

  B.When a transaction intends to change but not read data.

  C.When a transaction intends to read but not change data.

  D.When a transaction intends to change the system catalog.

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• 3Which statement will prevent concurrent application processes from performing anything other than read-only operations against a table named TAB1、

  A.LOCK TABLE tab1 IN READ MODE

  B.LOCK TABLE tab1 IN SHARE MODE

  C.LOCK TABLE tab1 IN EXCLUSIVE MODE

  D.LOCK TABLE tab1 IN READ-ONLY MODE

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• 4Application APP_A is performing updates to table TAB1 using the cursor stability (CS) isolation level. If application APP_B wants to retrieve all rows from table TAB1 without waiting for application APP_A to finish making updates, what isolation level must application APP_B use、

  A.Read Stability (RS)

  B.Repeatable Read (RR)

  C.Uncommitted Read (UR)

  D.Cursor Stability (CS)

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• 5Which type of lock allows the lock owner and all concurrent applications to read, but not update, the locked data、

  A.Share (S)

  B.Update (U)

  C.Exclusive (X)

  D.Intent Exclusive (IX)

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• 6Which operation normally does NOT require an exclusive lock、

  A.BIND

  B.DROP

  C.GRANT

  D.SELECT

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• 7When a COMMIT statement is executed, what happens、

  A.All locks held on the database are automatically released.

  B.Data stored in global temporary tables is automatically deleted.

  C.Open cursors defined WITH HOLD are closed, but their data is retaine

  D.D. The current transaction is terminated and a new transaction boundary is started.

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• 8Which command is used to back out a subset of database changes that have been made within a unit of work、

  A.COMMIT

  B.ROLLBACK

  C.COMMIT TO SAVEPOINT

  D.ROLLBACK TO SAVEPOINT

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• 9An SQL function designed to convert temperatures from Fahrenheit to Celsius was created as follows:  CREATE FUNCTION conv_temp(IN temp_f FLOAT)  RETURNS INTEGER  NO EXTERNAL ACTOIN  SPECIFIC convert_ftoc  RETURN INT((temp_f-32)/1.8) How can this function be used to convert average temperature (AVG_TEMP) data stored in a table called CLIMATE_INFO、

  A.CALL conv_temp(climate_info.avg_temp);

  B.CALL convert_ftoc(climate_info.avg_temp);

  C.SELECT conv_temp(avg_temp) FROM climate_info;

  D.SELECT convert_ftoc(avg_temp) FROM climate_info;

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• 10If a table named MY_TAB contains 100 rows and the following statement is executed:  DELETE FROM   (SELECT * FROM my_tab   ORDER BY col1 DESC   FETCH FIRST 5 ROWS ONLY) AS tmp; What will happen、

  A.The last 5 rows in the table will be deleted.

  B.The first 5 rows in the table will be deleted.

  C.The statement will fail because a subquery cannot be used with a DELETE statement.

  D.The statement will fail because a table name was not specified with the DELETE statement.

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