Display zero by using count(*) if no result returned for a particular case

Question

I have a query like this that returns number of rows for each case in city .

select 
    case edition_id 
        when 6 then \'DELHI\' 
        when 50 then         


        

Answer 1

I would insert the cities into a temporary table, then do a LEFT JOIN with the grouping query as follows:

CREATE TABLE #cities (edition_id INT, city VARCHAR(16))
INSERT INTO #cities VALUES(6, 'DELHI')
INSERT INTO #cities VALUES(50, 'AHMEDABAD')
INSERT INTO #cities VALUES(4, 'HYDERABAD')
INSERT INTO #cities VALUES(25, 'KOLKATA')
INSERT INTO #cities VALUES(51, 'BANGALORE')
INSERT INTO #cities VALUES(5, 'MUMBAI')
INSERT INTO #cities VALUES(24, 'CHENNAI')

select 
    c.city 'City', 
    ISNULL(t.Total, 0) 'Total'
from 
    #cities c
    LEFT JOIN (
        SELECT 
            edition_id, count(*) as Total 
        #tmptab1 
        GROUP BY edition_id
    ) AS t
    ON c.edition_id = t.edition_id

drop table #tmptab1
drop table #cities

BTW, it would make sense to have #cities as a normal table so that you don't need to create it everytime the query runs.