Question

I am creating a report orders by town.

SELECT S.city, count(*) as NumOfOrders
    FROM Shop as S
    LEFT JOIN orders O ON O.ShopID = S.ShopID
WHERE O.status = 4
Group by S.city

The result display something like this:

Town 1  |   53
Town 2  |   45
Town 3  |   64

It work fine but I want to display all towns even no orders?

Expected Result:

Town 1  |   53
Town 2  |   45
Town 3  |   64
Town 4  |   0
Town 5  |   0

I have tried replacing LEFT JOIN to RIGHT JOIN, that dont even work. Same result.

Answer 1

Though you are using a LEFT JOIN, you are using the o.statu column in a Where Clause and hence the rows with null values (cos of left join) will be dropped.

Try this:

SELECT S.city, 
        SUM 
        (
        CASE 
            WHEN ISNULL(O.status) THEN 0
            ELSE 1
        END  
        ) as NumOfOrders     
    FROM Shop as S  LEFT JOIN orders O 
      ON O.ShopID = S.ShopID 
 WHERE IFNULL(O.status, 4) = 4 
    GROUP BY S.city