将Perl正则表达式转换为SQL正则表达式

Question

I need to use Perl regular expressions in a Firebird database.

Firebird RDBMS does support regular expressions by providing a SIMILAR TO -condition . Unfortunately, the SQL regular expression syntax in Firebird differs from Perl syntax.

Is it possible to convert Perl regular expressions to SQL regular expressions? I do not need full compatibility but at least quantifiers and character classes should be convertible.

Answer 1

[I] do not need full compatibility but at least quantifiers and character classes should be convertible.

You are lucky, you may use character classes, ? , * , + , {exact_occurrences_number} , {min,} , {min,max} quantifiers with Firebird SIMILAR TO regex syntax .

The only trouble are Unicode category/property classes, you may only use POSIX character classes there:

<predefined class name> ::= ALPHA | UPPER | LOWER | DIGIT
| ALNUM | SPACE | WHITESPACE

Answer 2

I came to the following replacement rules (the order matters) to convert most Perl regular expressions to SQL syntax:

At first, SQL special characters have to be escaped:

1. _ > \\_
2. % > \\%

Then, Perl special characters and character classes have to be replaced.

3. . > _
4. \\d > [:digit:]
5. \\D > [^[:digit:]]
6. \\w > [^[:whitespace:]]
7. \\W > [:whitespace:]
8. \\s > [:whitespace:]
9. \\S > [^[:whitespace:]]

Note: The default Perl escape character \\ is used for SIMILAR TO here.

Feel free, to extend my answer with further possible replacements.