Mysql Select Query problem

I am using this below given query:

SELECT o.orders_id, o.customers_name, o.customers_id, o.payment_method, o.google_order_id, o.date_purchased, o.last_modified, o.currency, o.currency_value, s.orders_status_name
FROM orders o, orders_status s, customers c
WHERE o.customers_id = c.customers_id
AND o.orders_status = s.orders_status_id
AND c.customers_firstname = Nisha
OR c.customers_lastname = Nisha
OR c.customers_email_address = Nisha
OR c.customers_telephone = Nisha

and it gives me error as :#1054 - Unknown column 'Nisha' in 'where clause'

Y is it so? could some one guide me to resolve this?

It looks like you simply need to enclose Nisha in quotes: 'Nisha'

...
AND c.customers_firstname = 'Nisha'
OR c.customers_lastname = 'Nisha'
OR c.customers_email_address = 'Nisha'
OR c.customers_telephone = 'Nisha'

In addition, although not related to this error, note that you should probably group AND/OR conditions of the WHERE conditions in parenthesis:

WHERE (  o.customers_id = c.customers_id AND
         o.orders_status = s.orders_status_id
      ) AND
      (
         c.customers_firstname = 'Nisha' OR
         c.customers_lastname = 'Nisha' OR
         c.customers_email_address = 'Nisha' OR
         c.customers_telephone = 'Nisha'
      )