How to convert oracle characters to numbers?

In Oracle database, we can use the TO_NUMBER() function to convert character data type to numeric data type. Here are some detailed information about the TO_NUMBER() function:

1. Syntax: TO_NUMBER(expression, format_mask)
2. Parameters:

   expression: The expression or field to be converted to a number
   format_mask: Optional parameter used to specify the format of the input string. If not provided, the default number format from the database session settings will be used.

3. Return value: The TO_NUMBER() function returns a numerical value.
4. Warning: When converting characters to numbers, make sure that the input characters can be correctly converted to numbers, otherwise it will result in a failed conversion and an error message.

For example, in Oracle SQL, you can use the TO_NUMBER() function to convert a character into a number.

SELECT TO_NUMBER('12345') AS number_value
FROM dual;

The query will convert the characters ‘12345’ into the number 12345 and output it as the result.

In addition, if you need to process a string containing non-numeric characters, you can combine other functions to clean the string first, and then use the TO_NUMBER() function for conversion. For example, you can use the REGEXP_REPLACE() function to remove non-numeric characters.

SELECT TO_NUMBER(REGEXP_REPLACE('abc123def', '[^0-9]', '')) AS number_value
FROM dual;

The query above removes non-numeric characters from the string ‘abc123def’ and then converts it to a number.