To answer this question, we need to understand the concept of concatenation in SQL and the number of aliases used in the query.
The given query is:
SELECT address1||','||address2||','||address2 "Address" FROM employee;
In this query, we are concatenating three columns: address1, ',', and address2. We are using the pipe symbol (||) to concatenate these values.
We are also giving an alias "Address" to the concatenated result.
Now let's go through each option to determine the correct answer:
Option A) 1 - This option is incorrect because we are concatenating three columns, so there should be three columns in the result.
Option B) 2 - This option is incorrect because we are concatenating three columns, so there should be three columns in the result.
Option C) 3 - This option is correct because we are concatenating three columns, so there should be three columns in the result.
Option D) 4 - This option is incorrect because we are concatenating three columns, so there should be three columns in the result.
Therefore, the correct answer is C) 3. This option is correct because the query concatenates three columns, resulting in three columns in the output.