Does a ScriptService enabled WebService return JSON? If so how do you return database information?

I have read that when you use the [ScriptService] attribute in a WebService the webservice returns JSON.  Is that accurate?  If so what do you do when you want to return database queries from your web service?  I have mostly seen simple examples that add two numbers and return an int or simple hello world string.

Just wondering how to proceed.

Thank you.
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