How to use TO_NUMBER function to update columns of a table Using oracle pl/sql

Question

Hope you're doing well. I have a table with this structure :

Table1(Cust_No    Varchar2(50), 
       First_Name Varchar2(50), 
       Last_Name  Varchar2(50), 
       Error_Code number(1), 
       Error_Desc Varchar2(50))

At first , data will be inserted into column Cust_No and I should Update other columns of the table based on this column.The point is that all cust_No must have number format. For example Cust_No ='aa674' does not have a correct format. I need to write a query to update the table and set column First_Name='--' , columnLast_Name = '--', column Error_Code=1 and column Error_Desc='Incorrect format' for those Cust_No which has incorrect formats. I wanted to use TO_NUMBER() function but it gives me invalid number error. how may I solve this problem? Thanks in advance

Answer 1

You may use UDF to detect if a value can be treated as a number. Something like

CREATE OR REPLACE FUNCTION check_for_number( check_value IN VARCHAR2 )
RETURN VARCHAR2 DETERMINISTIC
IS
    tmp NUMBER;
BEGIN
    IF check_value IS NULL THEN
        RETURN 'Z';
    ELSE
        tmp := TO_NUMBER( check_value );
        RETURN 'Y';
    END IF;
EXCEPTION
    WHEN value_error THEN
        RETURN 'N';
    WHEN OTHERS THEN
        RETURN '?';
END check_for_number;

---

with test as ( select 1 id, '123' val from dual union all
               select 2   , '123asd'  from dual union all
               select 3   , 'asd'     from dual union all
               select 4   , NULL      from dual           )
select id, val, check_for_number(val)
from test;

ID  VAL     CHECK_FOR_NUMBER(VAL)
1   123     Y
2   123asd  N
3   asd     N
4   -       Z

Answer 2

As per your comment, requesting a regex solution:

update table1 set 
  error_code = 1
, error_desc = 'Incorrect format' 
where not regexp_like( cust_no, '^[0-9]+$' )

However, I would suggest that this is too little, too late.

You should not be allowing this defective data into the database in the first place! (Unless this is part of a migration exercise and this is a transitional table).

Your application should be detecting this bad formatting and not even saving the record to the database.

Second Thought:

Alternatively, put the check into the table definition

[Air Code; untested]

create table Table1
( Cust_No Varchar2(50) 
, CHECK( regexp_like( Cust_No '^[0-9]+$' )
. . . 

Third Thought:

If you customer number is, indeed, a number, then why are you storing it in the wrong Data Type?

create table Table1
( Cust_No  NUMBER 
. . .