Group by not returning 0 value - asp.net

Question

My table contains pk_id,reviewer_id,rating.
There are 4 type of rating.
1-very good.
2-good.
3-bad.
4-very bad.
I want to calculate how much rating given by each reviewer.
Means:
If Akee having id 200 has given 2 very good,4 good,3 bad and zero very bad rating to different code.
I want result
count--- rate
2---------1
4---------2
3---------3
0---------4
My query is
SELECT COUNT(RATE),RATE
FROM CODE_REVIEW WHERE CODE_REVIEWER_ID= 200
GROUP BY RATE;
It is showing result
count--- rate
2---------1
4---------2
3---------3
I want to show the fourth row that is 4 rating zero.
How can it be done??

Answer 1

If Rate is not the primary key in another table then you need define your own list of rates so MySQL knows what the permutations of rate are:
SELECT Rates.Rate,
COUNT(Code_Review.Rate) AS CountOfRate
FROM ( SELECT 1 AS Rate UNION ALL
SELECT 2 AS Rate UNION ALL
SELECT 3 AS Rate UNION ALL
SELECT 4
) AS Rates
LEFT JOIN Code_Review
ON Code_Review.Rate = Rates.Rate
AND CODE_REVIEWER_ID = 200
GROUP BY Rates.Rate

Answer 2

Try this query:
SELECT coalesce(c.cnt, 0), r.rate
FROM (SELECT 1 AS rate UNION ALL SELECT 2
UNION ALL SELECT 3 UNION ALL SELECT 4) AS r
LEFT JOIN (SELECT COUNT(RATE),RATE
FROM CODE_REVIEW WHERE CODE_REVIEWER_ID= 200
GROUP BY RATE) AS c
ON r.rate = c.rate;
The first subquery creates a list of possible rates. You can avoid it if you have a table which defines all rates;
Second subquery is yours;
LEFT JOIN guarantees that all rates will be shown;
coalesce() is needed to convert NULL into 0.

Answer 3

Assuming that you do not have a separate table where the rates are defined.
SElECT * from (
SELECT distinct(m.rate), countrate from code_review m
LEFT JOIN
(SELECT COUNT(rate) as countrate,rate FROM code_review
WHERE code_reviewer_id=200 GROUP BY rate) t
ON m.rate=t.rate) a

Answer 4

You could do it somthing like this
SELECT
rates.RATE
, SUM(COUNT) COUNT
FROM
(
SELECT 1 RATE, 0 COUNT UNION ALL
SELECT 2 RATE, 0 COUNT UNION ALL
SELECT 3 RATE, 0 COUNT UNION ALL
SELECT 4 RATE, 0 COUNT
) Rates
LEFT JOIN
(
SELECT
RATE
, COUNT(RATE) COUNT
FROM
CODE_REVIEW
WHERE
CODE_REVIEWER_ID= 200
GROUP BY RATE
) Ratings200
ON Ratings200.RATE = Rates.RATE

Answer 5

If you can, you should push to try to get it in column format as it is simple as:
SELECT
SUM(rate = 1) AS 1,
SUM(rate = 2) AS 2,
SUM(rate = 3) AS 3,
SUM(rate = 4) AS 4
FROM
code_review
WHERE
code_reviewer_id = 200
But if you really need a row format, you could do:
SELECT
a.rate,
COUNT(b.rate) AS cnt
FROM
(
SELECT 1 AS rate UNION ALL
SELECT 2 AS rate UNION ALL
SELECT 3 AS rate UNION ALL
SELECT 4 AS rate
) a
LEFT JOIN
code_review b ON a.rate = b.rate AND code_reviewer_id = 200
GROUP BY
a.rate

Answer 6

SELECT
Rate,
totCount
FROM
(
Select
Rate,
count(Rate) as totCount
from
Code_Review
where
CODE_REVIEWER_ID = 200
group by
Rate
union
select 4, 0
union
select 3, 0
union
select 2, 0
union
select 1, 0
) AS T
group by
T.Rate