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Database Interview Questions

Top data warehousing interview questions

  1. What is the data type of the surrogate key?
  2. What are the steps to build the data warehouse?
  3. What are the different architectures of data warehouse?
  4. What are the advantages data mining over traditional approaches?
  5. What is the difference between view and materialized view?
  6. What is the main difference between Inmon and Kimball philosophies of data warehousing?
  7. What is junk dimension? what is the difference between junk dimension and degenerated dimension?
  8. What is the definition of normalized and denormalized view and what are the differences between them
  9. Why fact table is in normal form?
  10. What is Difference between E-R Modeling and dimensional modeling.
  11. What is conformed fact?
  12. What are the methodologies of Data Warehousing.
  13. What is BUS Schema?
  14. What is Datawarehousing Hierarchy?
  15. What is data validation strategies for data mart validation after loading process
  16. What is a linked cube?
  17. What is meant by metadata in context of a Datawarehouse and how is it important?
  18. What is incremental loading?
  19. What is batch processing?
  20. What is cross-reference table?
  21. What is aggregate fact table?
  22. What are the possible data marts in Retail sales?
  23. What is the main difference between schema in RDBMS and schemas in DataWarehouse?
  24. What are the various ETL tools in the Market?
  25. What is Dimensional Modelling?
  26. What is VLDB?
  27. What is degenerate dimension table?
  28. What is ER Diagram?
  29. Difference between Snow flake and Star Schema. What are situations where Snow flake Schema is better than Star Schema to use and when the opposite is true?
  30. What is a CUBE in data warehousing concept?
  31. Differences between star and snowflake schemas?
  32. What are Datamarts?
  33. Can a dimension table contains numeric values?
  34. What is hybrid slowly changing dimension?

Top Oracle interview questions

  1. List components of an Oracle instance?
  2. Which background process and associated database component guarantees that committed data is saved even when the changes have not been recorded in the data files?
  3. What is the maximum number of database writer processes allowed in an Oracle instance?
  4. Which background process is not started by default when you start up the Oracle instance?
  5. Describe a parallel server configuration.
  6. Choose the right hierarchy, from largest to smallest, from this list of logical database structures.
  7. Which component of the SGA contains the parsed SQL code?
  8. Name the stages of processing a DML statement. What stages are part of processing a query?
  9. Which background process is responsible for writing the dirty buffers to the database files?
  10. Which component in the SGA has the dictionary cache?
  11. When a server process is terminated abnormally, which background process is responsible for releasing the locks held by the user?
  12. What is a dirty buffer?
  13. If you are updating one row in a table using the ROWID in the WHERE clause (assume that the row is not already in the buffer cache), what will be the minimum amount of information read to the database buffer cache?
  14. What happens next when a server process is not able to find enough free buffers to copy the blocks from disk?
  15. Which memory structures are shared? Name two.
  16. When a SELECT statement is issued, which stage checks the user’s privileges?
  17. Which memory structure records all database changes made to the instance?
  18. What is the minimum number of redo log files required in a database?
  19. When are the system change numbers assigned?
  20. Name the parts of the database buffer pool.
  21. List all the valid database start-up option?
  22. Which two values from the V$SESSION view are used to terminate a user session?
  23. To use operating system authentication to connect the database as an administrator, what should the value of the parameter REMOTE_LOGIN_PASSWORDFILE be set to?
  24. What information is available in the alert log files?
  25. Which parameter value is use to set the directory path where the alert log file is written?
  26. Which SHUTDOWN option requires instance recovery when the database is started the next time?
  27. Which SHUTDOWN option will wait for the users to complete their uncommitted transactions?
  28. How do you make a database read-only?
  29. Which role is created by default to administer databases?
  30. Which parameter in the ORAPWD utility is optional?
  31. Which priviledge do you need to connect to the database, if the database is started up by using STARTUP RESTRICT?
  32. At which stage of the database start-up is the control file opened?
  33. 13. User SCOTT has opened a SQL * Plus session and left for lunch. When you queired the V$SESSION view, the STATUS was INACTVE. You terminated SCOTT’s session in V$SESSION?
  34. Which command will “bounce” the database-that is, shut down the database and start up the database in a single command?
  35. 15. When performing the command SHUTDOWN TRANASACTIONAL, Oracle performs the following tasks in what order?
  36. How many panes are there in the Enterprise Manager console?
  37. Using SQL*Plus, list two options which show the value of the parameter DB_BLOCK_SIZE?
  38. When you issue the command ALTER SYSTEM ENABLE RESTRICTED SESSION, what happens to the users who are connected to the database?
  39. Which view has information about users who are ghranted SYSDBA or SYSOPER privilege?
  40. Which DB administration tools are included in the DBA Studio Pack?
  41. How many control files are required to create a database?
  42. Which environment variable or registry entry variable is used to represent the instance name?
  43. . What is the recommended configuration for control files?
  44. You have specified the LOGFILE clause in the CREATE DATABASE command as follows. What happens if the size of the log file redo0101.log, which already exists, is 10MB?
  45. Which command should be issued before you can execute the CREATE DATABASE command?
  46. Which initialization parameter cannot be changed after creating the database?
  47. What does OFA stand for?
  48. When creating a database, where does Oracle find information about the control files that need to be created?
  49. Which script creates the data dictionary views?
  50. Which prefix for the data dictionary views indicate that the contents of the view belong to the current user?
  51. Which data dictionary view shows information about the status of a procedure?
  52. How do you correct a procedure that has become invalid when one of the tables it is referring to was altered to drop a constraint?
  53. Which event trigger from the following cannot be created at the database level?
  54. How many data files can be specified in the DATAFILE clause when creating a database?
  55. Who owns the data dictionary?
  56. What is the default password for the SYS user?
  57. Which data dictionary view provides information on the version of the database and installed components?
  58. What is the prefix for dynamic performance views?
  59. Which clauses in the CREATE DATABASE command specify limits for the database?
  60. Which clauses in the CREATE DATABASE command specify limits for the database?
  61. Which optional component in the database creation process sets up functions and procedures to store, access, and analyze data needed for Geographical Information Systems (GIS)?
  62. What is the best method to rename a control file?
  63. What piece of information is not available in the control file?
  64. When you create a control file, the database has to be:
  65. Which data dictionary view provides the names of the control files?
  66. The initialization parameter file has LOG_CHECKPOINT_INTERVAL = 60; What does this mean?
  67. Which data dictionary view shows that the database is in ARCHIVELOG mode?
  68. What is the biggest advantage of having the control files on different disks?
  69. Which file is used to record all changes made to the database and is used only when performing an instance recovery?
  70. What will happen if ARCn could not write to a mandatory archive destination?
  71. How many ARCn processes can be associated with an instance?
  72. What are the valid status codes in the V$LOGFILE view?
  73. If you have two redo log groups with four members each, how many disks does Oracle recommend to keep the redo log files?
  74. What happens if you issue the following command? ALTER DATABASE ADD LOGFILE (’/logs/file1' REUSE, ‘/logs/file2' REUSE)
  75. Which two parameters cannot be used together to specify the archive destination?
  76. What packages are associated with the LogMiner utility?
  77. Querying which view will show whether automatic archiving is enabled?
  78. If you need to have your archive log files named with the log sequence numbers as arch_0000001, arch_0000002, and so on (zero filled, fixed width), what should be the value of the LOG_ARCHIVE_FORMAT parameter?
  79. List the steps needed to rename a redo log file.
  80. Which parameter is used to limit the number of dirty buffers in the buffer cache, thereby limiting the time required for instance recovery?
  81. Create a statement that will add a member /logs/redo22.log to log file group 2.
  82. When does the SMON process automatically coalesce the tablespaces?
  83. Which operation is permitted on a read – only tablespace?
  84. How would you drop a tablespace if the tablespace were not empty?
  85. Which command is used to enable the auto-extensible feature for a file, if the file is already part of a tablespace?
  86. 13. The database block size is 4KB. You created a tablespace using the following command. CREATE TABLESPACE USER_DATA DATAFILE ‘C:/DATA01.DBF’; If you create an object in the database without specifying any storage parameters, what will be the size of the third extent that belongs to the object?
  87. 14. Which statement is false? A. Dictionary-managed temporary tablespace can be made permanent. B. The size of the locally managed temporary tablespace file cannot be changed. C. Once created, the extent management of a tablespace cannot be altered. D. A locally managed permanent tablespace cannot be made temporary.
  88. Which statement is true regarding the SYSTEM tablespace? A. Can be me made read only. B. Can be offline. T C. Data files can be renamed. D. Data files cannot be resized
  89. What are the recommended INITIAL and NEXT values for a temporary tablespace, to reduce fragmentation?
  90. How would you determine how much sort space is used by a user session?
  91. 19. If you issue ALTER TABLESPACE USERS OFFLINE IMMEDIATE, which of the following statements is true? A. All data files belonging to the tablespace must be online. B. Does not ensure that the data files are available. C. Need not doe media recovery when bringing the tablespace online. D. Need to do media recovery when bringing the tablespace online.
  92. Place the following logical storage structures in order-from the smallest logical storage unit to the largest. A. Segment B. Block C. Tablespace D. Extent
  93. When a table is updated, where is the before image information (which can be used for undoing the changes) stored?
  94. Which parameter specifies the number of transaction slots in a data block?
  95. What happens if you create a rollback segment in the same tablespace where application data is stored? Choose the best answer. A. The tablespace will be fragmented. B. Performance improves, because when changes are made, undo information can be written to the same tablespace. C. There should be a minimum of two data files associated with the tablespaces when rollback segments are created. D. None of the above is true.
  96. 5. Which storage parameter is applicable only to rollback segments? A. PCTINCREASE B. MAXEXTENTS C. TRANASACTIONS D. None of the above.
  97. 6. Choose the statement used to manually de-allocate the extents used by a rollback segment. A. ALTER ROLLBACK SEGMENT R01 DEALLOCATE; B. ALTER ROLLBACK SEGMENT RO1 DROP EXTENTS; C. ALTER ROLLBACK SEGMENT RO1 SHRINK; D. ALTER ROLLBACK SEGMENT RO1 SIZE 10K.
  98. Which data dictionary view would you query to see the free extents in a tablespace?
  99. What is the minimum number of extents a rollback segment can have?
  100. Which portion of the data block stores information about the table having rows in this block?