PostgreSql constraint with Regex

I'm struggling with some PostgreSQL validation constraints with regular expressions.

For a name, I'm trying to define the allowed characters:

All letters, including diacritics, French and foreign (for example, I have Spanish names).
Apostrophe (single quote).
Single hyphen.
Space.

But a name must not begin or end with :

Apostrophe (single quote).
Single hyphen.
Space.

For this constraint, I think I'm ok with this since I can't insert any quoted characters:

CONSTRAINT CK_LASTNAME_BEG CHECK (LEFT(LASTNAME, 1) NOT IN (' ', '-', ''''))
CONSTRAINT CK_LASTNAME_END CHECK (RIGHT(LASTNAME, 1) NOT IN (' ', '-', ''''))

As for the allowed characters, it doesn't work. For the time being (I've only defined the French diacritical letters), I've set this:

CONSTRAINT CK_LASTNAME CHECK (LASTNAME ~ '[a-zéèàùâêîôûäëïöüçœA-ZÉÈÀÙÂÊÎÔÛÄËÏÖÜÇŒ'''' -]')

I can enter any character, a number, a parenthesis, etc.

Solution

I'd say that the constraint could simply be

CHECK (lastname ~ $pattern$^[[:alpha:]][- '[:alpha:]]*$$pattern$)

^ matches the beginning of the string
[[:alpha:]] matches a single alphabetic character
[- '[:alpha:]] matches an alphabetic character, space, hyphen or single quote
* means arbitrarily many of the previous pattern
$ matches the end of the string

There is one caveat: the meaning of [:alpha:] depends on your lc_ctype setting. If you created your database or defined your column with the C or POSIX locale, that will only match ASCII characters. For the best support of all possible characters, use a natural language ICU collation like "en-US-x-ico".