calculate average rating in sql server

Question

this is my table:

I want to fetch records of Those Vendor which contai

Answer 1

Use aggregate function AVG():

Try this:

SELECT u.id, u.ServiceDescription, u.Skills, u.fullname, u.email, AVG(ISNULL(rv.rating, 0)) averagerating
FROM UserDetails u 
INNER JOIN VendorInCategory v ON v.VendorId=u.Id 
INNER JOIN CategoryMaster c ON v.CategoryId=c.Id 
LEFT JOIN Review rv ON u.Id=rv.VendorId  
WHERE (u.ServiceDescription LIKE '%Plaster%' OR u.Skills LIKE '%Plaster%' OR 
       c.Name LIKE '%Plaster%')
GROUP BY u.id, u.ServiceDescription, u.Skills, u.fullname, u.email
ORDER BY averagerating DESC;

EDIT

Other solution to implement this:

SELECT u.id, u.ServiceDescription, u.Skills, u.fullname, u.email, 
       ISNULL(rv.averagerating, 0) averagerating
FROM UserDetails u 
INNER JOIN VendorInCategory v ON v.VendorId=u.Id 
INNER JOIN CategoryMaster c ON v.CategoryId=c.Id 
LEFT JOIN (SELECT rv.VendorId, AVG(rv.rating) averagerating FROM Review rv GROUP BY rv.VendorId) rv ON u.Id=rv.VendorId  
WHERE (u.ServiceDescription LIKE '%Plaster%' OR u.Skills LIKE '%Plaster%' OR 
       c.Name LIKE '%Plaster%')
ORDER BY ISNULL(rv.averagerating, 0) DESC;