REGEXP_LIKE help with literal single-quote

Question

I'm trying to write a check constraint to validate email addresses that may include an apostrophe in the email address. Such as joe.o'[email protected] Here is my sample setup:
create table emails
( email_address varchar2(150)
insert into emails values('[email protected]') ;
insert into emails values('[email protected]') ;
insert into emails values('joey.o''[email protected]') ;
commit;
sql> select * from emails;
EMAIL_ADDRESS
[email protected]
[email protected]
joey.o'[email protected]
alter table emails add constraint email_address_format_ck
    CHECK ( REGEXP_LIKE ( email_address, '^[a-z0-9._%-]\'?+@[a-z0-9._%-]+\.mil$','c'));
ERROR at line 2:
ORA-00911: invalid characterIt doesn't like *\'?*
My understanding is this means one or more single-quotes. Anyone know the correct syntax to accept apostrophes?

Answer 1

Hi,
jimmyb wrote:
... insert into emails values('joey.o''[email protected]') ;
That's the correct way (actually, that's one correct way) to include a single-quote in a string literal: use 2 single-quotes in a row.
... alter table emails add constraint email_address_format_ck
CHECK ( REGEXP_LIKE ( email_address, '^[a-z0-9._%-]\'?+@[a-z0-9._%-]+\.mil$','c'));Here, the 2nd argument to REGEXP_LIKE is a string literal, just like 'joey.o''[email protected]' was a string literal.
To include a single-quote in the middle of this string literal, do the same thing you did before: use 2 of them in a row:
CHECK ( REGEXP_LIKE ( email_address, '^[a-z0-9._%''-]+@[a-z0-9._%-]+\.mil$','c'));There were a couple of other problems, too.
I'm sure you meant for the apostrophe to be inside the square brackets. Inside square brackets, \ does not function as an escape character. (Actually, single-quote has no special meaning in regular expressions, so there's no need to escape it anyway.)
I'm not sure what the '?' mark was doing; I left it out.
Of course, you'll have trouble adding the CHECK constraint if any existing rows violate it.
Edited by: Frank Kulash on Feb 10, 2012 6:52 PM