Formatting numbers to add leading zeros can be done in SQL Server. It is just simple. Lets create a new table and see how it works:


CREATE TABLE Numbers(Num INT);
Table Created.

Lets insert few values and see:
  INSERT Numbers VALUES('12');
  INSERT Numbers VALUES('112');
  INSERT Numbers VALUES('12');
  INSERT Numbers VALUES('122');
  INSERT Numbers VALUES('122');
1 row(s) affected.
1 row(s) affected.
1 row(s) affected.
1 row(s) affected.
1 row(s) affected.

Now we can see how the numbers are formatted with 6 digits, if it has less than 6 digits it will add leading zeros.
Data:

SELECT * FROM Numbers;

Num
12
112
12
122
122

Formatting:
SELECT RIGHT('00000'+ CONVERT(VARCHAR,Num),6) AS NUM FROM Numbers;

NUM
000012
000112
000012
000122
000122
                                    (OR)
SELECT RIGHT(REPLICATE('0', 10) + CONVERT(VARCHAR, Num), 6) AS NUM FROM Numbers;
NUM
000012
000112
000012
000122
000122