qgis - How to format labels with leading zeroes?

I'm trying to display a number next to a symbol in QGIS 2.0.1 - The numbers are from an integer-field in a postgresql database.

The goal is that single digit numbers get a leading 0. Examples:

• 12 --> 12


• 10 --> 10


• 9 --> 09


• 0 --> 00

In the menu

 layer properties --> labelling --> formating

I switch on "number formatting" and then enter a custom expression. I tried these two codes with various combinations of ", ' and more brackets, but none of them work:

• 
  

  1

  
  

  CASE
  
        WHEN "Value" <10 THEN rpad("Value", 2, 0)
  
  
  END
  



• 
  

  2

  
  

  CASE
  
        WHEN "Value" <10 THEN "0" || "Value"
  
  END
  
  

EDIT:

For any other person having trouble with this: Turn of "number formatting". It seems to be the reason why leading zeros are removed from the rpad function.

Enter the following in the regular "layer labeling" box:

  rpad("Field", 2, 0)

and everything will work fine. But if you also activate number formatting it will take away the leading zeros.

Answer

We have the rpad function for that:

rpad('1', 2, '0') 
rpad('10', 2, '0')

result

01
10

rpad("yourcolumn", 2, '0')

rpad() function

Returns a string with supplied width padded using the fill character.

Syntax rpad(string, width, fill)

Arguments

string - is string. The string.
width - is int. The length of the new string.
fill - is char. The character to padd the remaining space with.

Example

rpad('Hello', 10, 'x') → 'xxxxxHello'