Better way of handling incorrect date format in a column with “char(10)” data type / TRY_CONVERT equivalent in PLSQL

Question

I have a source table with below structure:

create table customer_info
(customer_num    number,
 birth_date      char(10))

Unfortunately the birth_date column data type is char(10) instead of date. Some example data for this table would be like below:

customer_num    |  birth_date        
--------------------------------
  1             |  2001/01/01            
  1             |  2010/01/01            
  1             |  2021/01/01             
  1             |  12hhhhuu6   --> Incorrect date          
  1             |  2001/01/01            
  1             |  2001/23/01  --> Incorrect date

what I've done is writing a function to evaluate every single record and return it's correct format but as you know , using a function for every single record is not a good idea and it somehow kills performance. I was wondering if you could suggest a better way for this.

create or replace function new_to_date_en(d varchar2) return DATE
is
  v_date date;
begin
  select to_date(d,'yyyy/mm/dd' ) into v_date from dual;
  return to_date(d,'yyyy/mm/dd');
  exception when others then return to_dateto_date('2021/03/07', 'yyyy/mm/dd');
end;  

Using the function:

 select customer_num,
        new_to_date_en(birth_date)
 from customer_info;

There is a way in T-SQL COALESCE(TRY_CONVERT(date, @date, 111), '2012-01-01'). Is there a similar way in oracle plsql?

Thanks in advance

Answer 1

TRY_CONVERT is a function that is called for every record, how is that different?

Below works since 12.2:

SQL> alter session set nls_date_format='YYYY/MM/DD';

Session altered.

SQL> select cast('2021/03/07' as date default date'2012-01-01' on conversion error) from dual;

CAST('2021
----------
2021/03/07

SQL> select cast('X021/zz/99' as date default date'2012-01-01' on conversion error) from dual;

CAST('2021
----------
2012/01/01

SQL> select to_date('X021/zz/99' default date'2012-01-01' on conversion error, 'YYYY/MM/DD') from dual;

TO_DATE('X
----------
2012/01/01

SQL>

On your version, you can use your function.