To answer this question, you need to understand how to use the LIKE operator in SQL. The LIKE operator is used to search for a specified pattern in a column.

Let's go through each option to understand why it is correct or incorrect:

Option A) SELECT * FROM Persons WHERE FirstName LIKE 'a%' - This option is correct. The LIKE 'a%' condition will select all records from the 'Persons' table where the value of the 'FirstName' column starts with an 'a'.

Option B) SELECT * FROM Persons WHERE FirstName LIKE '%a' - This option is incorrect. The LIKE '%a' condition will select all records from the 'Persons' table where the value of the 'FirstName' column ends with an 'a', not starts with an 'a'.

Option C) SELECT * FROM Persons WHERE FirstName='a' - This option is incorrect. The = operator is used for exact matches. The condition FirstName='a' will select only the records where the value of the 'FirstName' column is exactly 'a', not those that start with an 'a'.

Option D) SELECT * FROM Persons WHERE FirstName='%a%' - This option is incorrect. The % wildcard character is used to match any sequence of characters. The condition FirstName='%a%' will select all records where the value of the 'FirstName' column contains an 'a' anywhere, not just at the beginning.

The correct answer is Option A) SELECT * FROM Persons WHERE FirstName LIKE 'a%'. This option is correct because it selects all records from the 'Persons' table where the value of the 'FirstName' column starts with an 'a'.

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To answer this question, you need to understand the LEN function in SQL.

The LEN function is used to return the number of characters in a specified string. In this case, the specified string is the variable @val, which is set to ' SQL is cool '.

The LEN function will count all characters in the string, including leading and trailing spaces. Therefore, the output of the query select LEN(@val) will be the total number of characters in the string, which is 12.

So, the correct answer is C) 12.

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To determine the length of the variable @c, we need to understand how the LEN() function works in SQL.

In SQL, the LEN() function is used to return the number of characters in a string. It counts the number of characters, including spaces and special characters.

In the given code snippet, the variable @c is declared as a varchar(8000). This means it can hold a maximum of 8000 characters.

The code then sets the value of @c to N'hello' + replicate('-',8000). Here, replicate('-',8000) is used to repeat the dash symbol "-" 8000 times. The resulting string is concatenated with the string "hello".

Since the LEN() function counts the number of characters in a string, it will count all the characters in @c, including the "hello" string and the repeated dashes.

Therefore, the length of @c will be the sum of the length of "hello" (5 characters) and the length of the repeated dashes (8000 characters).

So the correct answer is:

B. 4000

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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'.

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To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) to_char - This option is correct because the to_char function in SQL can operate on any datatype. It is used to convert a value of any datatype to a character string.

Option B) max - This option is incorrect because the max function in SQL is used to return the maximum value of a specified column. It operates on numeric data types, not any datatype.

Option C) rollup - This option is incorrect because the rollup function in SQL is used to generate subtotals and grand totals in a result set. It operates on grouping sets, not any datatype.

Option D) cube - This option is incorrect because the cube function in SQL is used to generate all possible combinations of a specified set of expressions. It operates on grouping sets, not any datatype.

The correct answer is Option A) to_char. This option is correct because the to_char function can operate on any datatype and convert it to a character string.

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To answer this question, you need to understand the differences between the commands DROP, DELETE, and TRUNCATE in the context of deleting data from a table.

Option A) DROP - This option is incorrect because the DROP command is used to delete an entire table or database object, including its structure. It does not specifically delete data from a table without affecting the rollback segment.

Option B) DELETE - This option is incorrect because the DELETE command is used to delete specific rows from a table based on a condition. It does write to the rollback segment to allow for a rollback operation if needed.

Option C) TRUNCATE - This option is correct because the TRUNCATE command is used to delete all data from a table, but it does not write to the rollback segment. TRUNCATE is a DDL (Data Definition Language) command that is faster than DELETE because it deallocates the data pages and resets the highwater mark, freeing the space for reuse.

Option D) REMOVE - This option is incorrect because the REMOVE command is not a valid command in most database systems.

Option E) NONE OF THE ABOVE - This option is incorrect because option C (TRUNCATE) is the correct answer.

The correct answer is C) TRUNCATE. This option is correct because it deletes all data from a table without writing to the rollback segment.

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