Mysql: Group by Hour, 0 if no data

Question

I have the following query:

SELECT count(*) as \'totalCalls\', HOUR(`end`) as \'Hour\'
FROM callsDataTable 
WHERE company IN (
    SELECT number 
    FROM pr         


        

Answer 1

You need a Hour table and then do a left Outer Join with the Hour_table.

Which will ensure that all hours will be returned. If hour doesn't exists in callsDataTable then count will be 0.

Hours Table

create table hours_table (hours int);

insert into hours_table values(0);
insert into hours_table values(1);
 ...
insert into hours_table values(23);

Query:

SELECT count(HOUR(`end`)) as 'totalCalls', HT.Hours as 'Hour'
FROM Hours_table HT left Outer join callsDataTable CD
on HT.Hours = HOUR(`end`)
WHERE company IN (
    SELECT number 
    FROM products 
    WHERE products.id IN (@_PRODUCTS)) 
    AND YEAR(`end`) = @_YEAR AND MONTH(`end`) = @_MONTH 
 group by HT.Hours