How do I place leading zeros for numbers less than 10 without affecting those 10+?

Question

Probably a newb question, but...

I have a table with a VARCHAR field containing numbers 1 through 300. I need to place a leading zero in front of any numbers less than 10 while retaining the original number if it is 10 or greater (i.e. 1=01, 10=10 and 300=300).

SELECT DISTINCT RIGHT('0'+CONVERT(VARCHAR,[FacilityCode]),3) FROM...

This returns 1=01, 10=010 and 300=300 (using the same examples as above)

EDIT: I'm trying to do this within a query so that I can do lookups without altering either table.

Can someone lend a brother a hand here? My brain just ain't working.

Answer 1

The safest way is probably to only add zeroes when the length of the column is 1 character:

UPDATE
   Table
SET
   MyCol = '0' + MyCol
WHERE
   LEN(MyCol) = 1;

This will cover all numbers under 10 and also ignore any that already have a leading 0.

EDIT

To just select the data try:

SELECT
   MyColPadded = CASE WHEN LEN(MyCol) = 1 THEN '0' + MyCol ELSE MyCol END
FROM
   MyTable;

Answer 2

(it looks from your example code that you are using MS SQL Server, but you should add an appropriate tag (and/or body text) to your question to indicate this if so, or if not which DBMS you are actually using)

Any of the options above should work fine, I would generally use the "prefix 0s then use RIGHT() option as you have but the others are perfectly valid), but a word of warning if you expect new rows (or updates to existing rows) to contain low numbers - if that is possible then you will end up with unpadded values creeping back in. To avoid this you could use either an AFTER or INSTEAD OF trigger to force values into the right format as they are inserted/updated to stop the problem coming back (without needing to change all code points that save to that table). Be careful to verify performance though: triggers can be very powerful but it is also easy to create a performance nightmare with them.

Answer 3

You can use a case statement for this, if it must be formatted in the database and you can't persist it.

Select case when len(facilityCode) = 1 then 
          '0' else '' end + facilityCode as facilityCode
From YourTable

It sounds like you are doing this as a FK, if so you can't have a FK constraint on a calculation. To make doing the join easier, you might consider a calculated column.

 ALTER TABLE yourTable 
    ADD cFacilityCode AS (
      case when len(facilityCode) = 1 then '0' else '' end + facilityCode);

Answer 4

If you wanted a 3 digit number try this.

SELECT DISTINCT 
RIGHT('000'+CAST(ISNULL([FacilityCode],0) AS VARCHAR),3) 
FROM...

Result: 1=001, 10=010 and 300=300

An 8 digit number would be:

SELECT DISTINCT 
RIGHT('00000000'+CAST(ISNULL([FacilityCode],0) AS VARCHAR),8) 
FROM...

Result: 1=00000001, 10=00000010 and 300=00000300

This has the advantage of working with subqueries:

SELECT t_lac.FORCE_OVERWRITE
            , ISNULL(lay.ID,0) AS lacIDLayout
            --, t_lac.lacName
            , CASE WHEN t_lac.lacIDControlType = 18
                THEN 'PAN' + RIGHT('000' + CAST(ISNULL((SELECT ID FROM Layout l WHERE l.layName = t_lac.lacName),0) AS VARCHAR),3) + '_' + t_lac.lacName
                ELSE t_lac.lacName
                END AS lacName
            , t_lac.lacIDControlType
            , t_lac.lacStyle 
            FROM @T_LayoutControl t_lac
            LEFT JOIN Layout lay ON lay.layName = t_lac.layName

Answer 5

UPDATE MyTable
SET MyColumn = '0' + Mycolumn
WHERE MyColumn < '10'
AND MyColumn NOT LIKE '0%';

Answer 6

declare @num varchar(50) = '7'
select case when @num<100 
            then RIGHT('00'+ CONVERT(VARCHAR(50),@num),2) 
            else CONVERT(varchar(50),@num) end