How do I extract indian rupee sign ₹ from a number or string

Basically, change your database.
Don't store numeric values as strings at all: store them as INT, FLOAT, or DECIMAL - and the latter is the most appropriate for currency values.
And remove the currency symbol in your presentation code when you validate and convert the user input, so that only value numbers can reach the DB.

If you don't, you get problems: what if a user enters a US$ or £ value instead? You can't just "remove the currency symbol" because the number isn't valid as Rupees anyway if it started out in a different currency - and the only way to fix that is at the point when the user enters the data.

And than there's using the data later: you can't do maths with strings: so even if you take off the currency indicator, every time you want to work out a total (price per * units sold for an invoice for example) you have to convert the string to a number, do the maths, and then use it - and at that point you find the user typed "₹12,3R,567" by mistake and you don't know what the value should have been. And that could be months later!

So always store data in the most appropriate format: numbers in numeric fields, dates in date / time fields. It ensures your data integrity, and saves you a huge amount of work later!