Multiple choice technology databases

What is the Result of the following 'AXA'||NULL||'US' ?

  1. Error

  2. NULL

  3. AXA US

  4. AXAUS
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D Correct answer
Explanation

In Oracle SQL, the concatenation operator (||) treats NULL as an empty string, not as a NULL value that propagates. Therefore 'AXA'||NULL becomes 'AXA', and then ||'US' produces 'AXAUS'. This is different from arithmetic operations where NULL + anything = NULL.

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