Multiple choice technology databases

The o/p of the below query would be.. select nvl('abc','a') from dual union all select nvl('abc',0) from dual minus select replace('abc','a','a') from dual

  1. No rows returned

  2. abc

  3. Two rows of value 'abc'

  4. Error: Syntax error

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A Correct answer
Explanation

Both NVL queries return 'abc' (non-null value). The REPLACE query also returns 'abc'. UNION ALL combines the two 'abc' rows, then MINUS removes rows matching the REPLACE result. Since both are 'abc', MINUS removes everything, leaving no rows.