To answer this question, let's understand the function SUBSTRING() in SQL.
The SUBSTRING() function is used to extract a substring from a given string. It takes three parameters: the input string, the starting position of the substring, and the length of the substring.
In the given question, the input string is '123456', the starting position is 0, and the length of the substring is 3.
Using these parameters, the SUBSTRING() function will extract a substring from the input string starting at position 0 and with a length of 3.
Now, let's go through each option to determine the correct output:
Option A) 123 - This option is incorrect because the starting position is 0, which means the substring will start from the first character of the input string. Therefore, the output will not include the first character '1'.
Option B) 12 - This option is correct. The starting position is 0, so the substring will start from the first character '1'. The length of the substring is 3, so it will include the first two characters '1' and '2'.
Option C) 123456 - This option is incorrect because the length of the substring is 3. Therefore, the output will not include the entire input string.
Option D) 456 - This option is incorrect because the starting position is 0, so the substring will start from the first character '1'. The length of the substring is 3, so it will not include the characters '4', '5', and '6'.
The correct answer is Option B) 12. This option is correct because the substring will start from the first character '1' and have a length of 3, including the characters '1' and '2'.