I want to get value of remote site url in salesforce (Ex: I want to get http://abc.com like image below). How can I use query SOQL in APEX to get it?
You can use ToolingAPI to access the RemoteSiteSettings. In developer you can try to query like below.
select id, SiteName, EndpointUrl from RemoteProxy
In the above query EndpointUrl is field which you are looking for.
You need to check the "Use Tooling API" check box to true else you will not get result.