CHR FAQS

1. What is the purpose of the CHR function in Oracle?

The CHR function in Oracle is used to return the character corresponding to a given ASCII code. It allows you to convert numeric ASCII values into their character representations.

 

2. What range of numbers can be used with CHR?

The valid range for CHR is from 0 to 255, which corresponds to the extended ASCII character set. Values outside this range will result in an error.

 

3. What is the behavior of CHR when the number is NULL?

If the number argument passed to CHR is NULL, the function will return NULL as the result.

 

4. Can CHR return non-printable characters?

Yes, CHR can be used to return non-printable characters such as control characters. For example:

• CHR(10): Newline (Line feed)
• CHR(9): Horizontal tab
• CHR(13): Carriage return

These can be used to manipulate text formatting.

 

5. Can I use negative numbers with CHR?

No, CHR only accepts positive integers within the range 0 to 255. Using negative numbers will result in an error.

 

6. What happens if I use CHR with a number larger than 255?

If the number provided is greater than 255, the CHR function will result in an error. Oracle can only handle ASCII codes from 0 to 255.

 

7. How do I use CHR for inserting control characters?

CHR is useful for inserting control characters into strings for formatting purposes. Some examples include:

• CHR(10): Newline (Line feed)
• CHR(9): Tab
• CHR(13): Carriage return

Example:

SELECT 'Hello' || CHR(10) || 'World' FROM dual;

This will insert a newline between the words "Hello" and "World".

 

8. Can I use CHR to format output in SQL queries?

Yes, CHR can be used to format the output of your queries by inserting special characters such as spaces, tabs, or newlines.

Example:

SELECT 'Item' || CHR(9) || 'Price' || CHR(9) || 'Quantity' FROM dual;

This inserts tab spaces between "Item", "Price", and "Quantity".

 

9. How is CHR different from CHAR?

• CHR(number): Returns the character corresponding to an ASCII code. This function works with numeric ASCII values.
• CHAR(string): Returns the ASCII code of the first character of the provided string.

 

10. What happens if I pass a negative or out-of-range value to CHR?

Passing a value less than 0 or greater than 255 will result in an error. The CHR function only supports values within the 0-255 range.

 

11. How can CHR be used in string manipulation?

You can use CHR in combination with other functions such as CONCAT to build strings dynamically, especially when inserting control characters for formatting or splitting data.

Example:

SELECT 'Hello' || CHR(13) || 'World' FROM dual;

This would insert a carriage return between "Hello" and "World".

 

12. Can I use CHR for generating files or reports?

Yes, CHR is often used to format strings in reports or when generating text-based files such as CSV, where you need control characters like tabs or newlines to separate data fields.

 

13. What is the result of CHR(0)?

CHR(0) returns the null character, which is a non-printable control character. It doesn’t show a visible symbol but exists within the extended ASCII set.

 

14. Is CHR case-sensitive?

The CHR function operates based on ASCII values, and ASCII itself is case-sensitive. For example, CHR(65) returns 'A' (uppercase), while CHR(97) returns 'a' (lowercase).

 

15. Can CHR be used with any character encoding?

CHR works based on the ASCII character set. For characters outside the standard ASCII range (like Unicode characters), you may need to use other functions such as NCHR or manage encoding formats properly in your database.