Removing leading zeros from varchar sql developer

oracle, sql

Solution

Oracle has built-in `TRIM` functions for strings. Assuming you have a string like `'00012345'` and you want to keep it as a string, not convert it to an actual `NUMBER`, you can use the `LTRIM` function with the optional second `set`parameter specifying that you're triming zeros:

select ltrim('000012345', '0') from dual;

LTRIM
-----
12345

If you might also have leading spaces you can trim both in one go:

select ltrim(' 00012345', '0 ') from dual;

LTRIM
-----
12345

You could also convert to a number and back, but that seems like a lot of work unless you have other formatting that you want to strip out:

select to_char(to_number('000012345')) from dual;

Incidentally, the immediate reason you get the ORA-01722 from your first attempt is that you're using the numeric `+` operator instead of Oracle's string concentenation operator `||`. It's doing an implicit conversion of your string to a number, which it seems you're trying to avoid, and the implicit conversion of the single space - whatever that is for - is causing the error. (Possibly some of your values are not, in fact, numbers at all - another example of why numbers should be stored in `NUMBER` fields; and if that is the case then converting (or casting) to a number and back would still get the ORA-01722). You'd get the same thing in the second attempt if you were using `LENGTH` instead of `LEN`. Neither would work anyway as `INSTR` doesn't recognise regular expressions. You could use `REGEXP_INSTR` instead, but you'd be better off with @schurik's `REGEXP_REPLACE` version if you wanted to go down that route.

I'm not sure I understand your question edit. It looks like your insert can be simplified to:

INSERT INTO temp_table (columnNeedTrim, column2, column3, column4, column5)
SELECT LTRIM(table1.columnNeedTrim, '0 '),
    table1.column2,
    table1.column3,
    table1.column4,
    table1.column5
FROM table1
INNER JOIN table2 ON table2.columnNeedTrim = table1.columnNeedTrim
WHERE NOT EXISTS (
    SELECT * FROM temp_table
    WHERE columnNeedTrim = LTRIM(t42.columnNeedTrim, '0 '));

(I don't understand why you're doing a subquery in your version, or why you're getting the trimmed value from another subquery.)

You could also use `MERGE`:

MERGE INTO temp_table tt
USING (
    SELECT LTRIM(t42.columnNeedTrim, '0 ') AS columnNeedTrim,
        t42.column2,
        t42.column3,
        t42.column4,
        t42.column5
    FROM t42 
    INNER JOIN t43 ON t43.columnNeedTrim=t42.columnNeedTrim
) sr
ON (sr.columnNeedTrim = tt.columnNeedTrim)
WHEN NOT MATCHED THEN
INSERT (tt.columnNeedTrim, tt.column2, tt.column3, tt.column4, tt.column5)
VALUES (sr.columnNeedTrim, sr.column2, sr.column3, sr.column4, sr.column5);

Problem

Original source