Oracle Interview Question and Answers

51. What are the components of physical database structure of Oracle database?
  Oracle database is comprised of three types of files. One or more data files, two are more redo log files, and one or more control files.
52. What is DECODE function used for?
  DECODE is used to decode a CHAR or VARCHAR2 or NUMBER into any of several different character strings or numbers based on value. That is DECODE does a value-by-value substitution.
53. What is the default return value of a function?
  The default return value from a function is int. In other words, unless explicitly specified the default return value by compiler would be integer value from function.
54. What is the difference between oracle,sql and sql server?
  • Oracle is based on RDBMS.
  • SQL is Structured Query Language.
  • SQL Server is another tool for RDBMS provided by MicroSoft.
55. How you will avoid your query from using indexes?
  By changing the order of the columns that are used in the index, in the Where condition, or by concatenating the columns with some constant values.
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