原文出处：http://mfm088.itpub.net/post/22599/250400
Oracle/PLSQL: Lpad Function

In Oracle/PLSQL, the lpad function pads the left-side of a string with a specific set of characters.

The syntax for the lpad function is:

lpad( string1, padded_length, [ pad_string ] )

string1 is the string to pad characters to (the left-hand side).

padded_length is the number of characters to return. If the padded_length is smaller than the original string, the lpad function will truncate the string to the size of padded_length.

pad_string is optional. This is the string that will be padded to the left-hand side of string1. If this parameter is omitted, the lpad function will pad spaces to the left-side of string1.

For example:

lpad('tech', 7);	would return ' tech'
lpad('tech', 2);	would return 'te'
lpad('tech', 8, '0');	would return '0000tech'
lpad('tech on the net', 15, 'z');	would return 'tech on the net'
lpad('tech on the net', 16, 'z');	would return 'ztech on the net'