Multiple choice technology databases

select dummy from dual ?

  1. NULL

  2. Error: invalid identifier

  3. X

  4. Error: invalid SQL Statemet

  5. A
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C Correct answer
Explanation

Oracle's DUAL table contains a pseudo-column called DUMMY. The DUMMY column always contains the value 'X'. Selecting this column returns X - this is documented Oracle behavior for backwards compatibility.

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