Top 10 Oracle Interview Questions and Answers For 1 year Experienced

  1. Difference between varchar and varchar2 data types?
    Varchar can store upto 2000 bytes and varchar2 can store upto 4000 bytes. Varchar will occupy space for NULL values and Varchar2 will not occupy any space. Both are differed with respect to space.
  2. In which language Oracle has been developed?
    Oracle has been developed using C Language.
  3. What is RAW datatype?
    RAW datatype is used to store values in binary data format. The maximum size for a raw in a table in 32767 bytes.
  4. What is the use of NVL function?
    The NVL function is used to replace NULL values with another or given value. Example is –
    NVL(Value, replace value)
  5. Whether any commands are used for Months calculation? If so, What are they?
    In Oracle, months_between function is used to find number of months between the given dates. Example is –
    Months_between(Date 1, Date 2)
  6. What are nested tables?
    Nested table is a data type in Oracle which is used to support columns containing multi valued attributes. It also hold entire sub table.
  7. What is COALESCE function?
    COALESCE function is used to return the value which is set to be not null in the list. If all values in the list are null, then the coalesce function will return NULL.
    Coalesce(value1, value2,value3,…)
  8. What is BLOB datatype?
    A BLOB data type is a varying length binary string which is used to store two gigabytes memory. Length should be specified in Bytes for BLOB.
  9. How do we represent comments in Oracle?
    Comments in Oracle can be represented in two ways –
    Two dashes(–) before beginning of the line – Single statement
    is used to represent it as comments for block of statement
  10. What is DML?
    Data Manipulation Language (DML) is used to access and manipulate data in the existing objects. DML statements are insert, select, update and delete and it won’t implicitly commit the current transaction.
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