正则表达式：获取所有单个字符，但不是在单引号之间

Question

I need a Regex expression to catch all colons in a string, but not when the colon is between single quotes, and then replace it with an at sign (@).

My test string is:

select id, :DATA_INI, ':DATA_INI', titulo, date_format(data_criacao,'%d/%m/%Y %H:%i') str_data_criacao
from v$sugestoes
where data_criacao between :DATA_INI AND :DATA_FIM
order by data_criacao

What I actually want is:

select id, @DATA_INI, ':DATA_FIM', titulo, date_format(data_criacao,'%d/%m/%Y %H:%i') str_data_criacao
from v$sugestoes
where data_criacao between @DATA_INI AND @DATA_FIM
order by data_criacao

I've tried this regex expression, but for some reason it doesn't catch the first colon:

/(?!'.*?):(?!.*?')/g

PS: there's a possibility of nested quotes and these strings can't be catched as well.

Anyone knows what I am missing here? I´m actually using C#.

Answer 1

This could do it:

:(?=([^']*'[^']*')*[^']*$)

RegEx tester

It only matches those colons that have an even number of quotes following it (positive look ahead). This also covers the case where quotes are escaped (for SQL) inside quoted string, as those are preceded by another quote and so keep the quote count even.

As stated in comments, this regex is rather inefficient because it scans some parts of the string multiple times: each time a colon is found, the rest of the string is scanned to see whether the number of (non-escaped) quotes is even.

But for SQL strings, which seems to be the types of strings you deal with, this should not be an issue, they are typically strings that are not extremely long, nor have hundreds of quotes or colons.

C# solution

Working from the above idea, you could use the following C# code:

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        // This is the input string we are replacing parts from.
        string input = "select id, :DATA_INI, ':DATA_INI', titulo, date_format(data_criacao,'%d/%m/%Y %H:%i') str_data_criacao\n"
            + "from v$sugestoes\n"
            + "where data_criacao between :DATA_INI AND :DATA_FIM AND ':TEST'\n"
            + "  and  'test ''string :DATA_INI '' :DATA_INI '\n"
            + "order by data_criacao";

        string output = Regex.Replace(input, ":(?=([^']*'[^']*')*[^']*$)", "@");

        Console.WriteLine(output);
    }
}

See it run on ideone.com .

Answer 2

Since you are using C#, try:

Regex.Replace(input, @"(?<!'):(\w+)", "@$1")

This will match all placeholders which are not directly preceeded by a ' (negative look behind).

Working example: https://dotnetfiddle.net/N43ipM