How to handle invalid date in oracle sql?

@hal.littel 

In Oracle SQL, you can handle invalid dates by using the TO_DATE function to convert a string into a date value. If the input string does not match the expected date format, Oracle will raise an error.

Here are a few ways to handle invalid dates in Oracle SQL:

1. Use exception handling: You can use a BEGIN...END block with an exception handler to catch any errors that occur when trying to convert a string to a date. For example:

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BEGIN
  SELECT TO_DATE('invalid_date_string', 'YYYY-MM-DD') INTO my_date FROM dual;
EXCEPTION
  WHEN others THEN
    dbms_output.put_line('Invalid date format');
END;

1. Use a case statement to handle invalid dates: You can use a case statement to check if the input string is a valid date before converting it. If the input string is not a valid date, you can return a default value or raise an error. For example:

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SELECT 
  CASE 
    WHEN REGEXP_LIKE('invalid_date_string', '^[0-9]{4}-[0-9]{2}-[0-9]{2}$') 
    THEN TO_DATE('invalid_date_string', 'YYYY-MM-DD') 
    ELSE NULL 
  END AS my_date
FROM dual;

1. Use a custom function: You can create a custom function that validates the input string and returns a valid date value. This function can handle different date formats and return a default date value if the input string is not a valid date. Here is an example of a custom function that handles invalid dates:

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CREATE OR REPLACE FUNCTION convert_to_date(date_string IN VARCHAR2) RETURN DATE IS
  my_date DATE;
BEGIN
  my_date := TO_DATE(date_string, 'YYYY-MM-DD');
  RETURN my_date;
EXCEPTION
  WHEN others THEN
    RETURN NULL;
END;

These are just a few ways to handle invalid dates in Oracle SQL. The best approach will depend on your specific requirements and the context of your query.