Question

In Oracle, when converting a number with a leading zero to a character, why does the leading number disappear? Is this logic Oracle specific, or specific to SQL?

Example:

SELECT TO_CHAR(0.56) FROM DUAL;
/* Result = .56 */

Answer 1

It’s the default formatting that Oracle provides. If you want leading zeros on output, you’ll need to explicitly provide the format. Use:

SELECT TO_CHAR(0.56,'0.99') FROM DUAL;

or even:

SELECT TO_CHAR(.56,'0.99') FROM DUAL;

The same is true for trailing zeros:

SQL> SELECT TO_CHAR(.56,'0.990') val FROM DUAL;

VAL
------
 0.560

The general form of the TO_CHAR conversion function is:

TO_CHAR(number, format)