Friday, 8 March 2013

PLSQL check my email adress...

PL SQL Code for checking mail adress

So you want to put some security check on you're mail input field...
As you know mail can consist letters, numbers and dots....
It must contain only one @ sign...
How would you check you're email?

I do check on two different ways

Simple way of checking allowed signs in mail

function f_emailok (i_email in varchar2) return boolean is
  l_dot    NUMBER;
  l_at     NUMBER;
  l_length NUMBER;
  l_dot    := instr(i_email ,'.');
  l_at     := instr(i_email,'@');
  l_length := length(i_email);
  IF ((l_dot = 0) OR (l_at = 0) OR (l_dot = l_at + 1) OR
     (l_at = 1) OR (l_at = l_length) OR (l_dot = l_length))
    RETURN (false);
  end if;
  IF instr(substr(i_email,l_at),'.') = 0 then
    RETURN (false);
  end if;
  return (true);
END f_emailok;

Let's explain code....

With instr function we are searching for sign in our string. In this case we search for . (dot), @ (at) and we are measuring length of our string input.
   l_dot    := instr(i_email ,'.');
we get some numeric value in our l_dot variable.
let's say i_email is filled with value
l_dot will pick up value 5 from i_email input cause dot sign is on the fifth place in our string.
after we pick up @ value on 11th sign in string and length of  our string we can do some logic.
We say if value of l_dot is 0 or l_at = 0 or there is @ sign behind dot or @ sign is on the first place or there is all string filled with @ or with dots return false.

We still need one more check. Is there anything behind @ sign 
   instr(substr(i_email,l_at),'.') = 0
if value is zero return false...

If everything goes correctly we return true value.

But there is one bug in code :) you can pass email in incorrect format...
Figure out which and how to solve it...


Now we check email format with OWA pattern integrated function  

function f_emailok (i_email in varchar2) return boolean is
         if owa_pattern.match(i_email,'\w{1,}[.,0-9,a-z,A-Z,_]\w{1,}\w{1,}[.,0-9,a-z,A-Z,_]\w{1,}'||
            '\@\w{1,}[.,0-9,a-z,A-Z,_]\w{1,}\.\w{1,}[.,0-9,a-z,A-Z,_]\w{1,}$') then
      end if;
      when others then
END f_emailok;

So what does this code do?
It searches for allowed signs in our code....
we pass some string and in order with our owa patterns we search if it consists of illegal characters...
here is list of pattern  

PLSQL list of pattern


  • ^ Matches the beginning of a line (or string)
  • $ Matches the end of a line (or string)
  • Quantifiers:
  • {n,m} Must match at least n times, but not more than m times
  • {n,} Must match at least n times
  • {n} Must match exactly n times.
  • * 0 or more occurances
  • + 1 or more occurances
  • ? 0 or 1 occurance(s)

Legal atoms:

  • . matches any character except \n
  • A list of characters in square brackets [] is a class of characters,
  • for example [0-9] indicates match any character from 0 to 9.
  • \n matches newlines
  • \t matches tabs
  • \d matches digits [0-9]
  • \D matches non-digits [^0-9]
  • \w matches word characters (alphanumeric) [0-9a-z_A-Z]
  • \W matches non-word characters [^0-9a-z_A-Z]
  • \s matches whitespace characters [ \t\n]
  • \S matches non-whitespace characters [^ \t\n]
  • \b matches on “word” boundaries (between \w and \W)
  • A backslashed x followed by two hexadecimal digits, such as \x7f,matches the character having that hexadecimal value.

  • A backslashed 2 or 3 digit octal number such as \033 matches the character with the specified value.

  • Any other “backslashed” character matches itself.


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