how to do get multiple columns + count in a single query? - sql

Question

I usually don't ask for "scripts" but for mechanisms but I think that in this case if i'll see an example I would understand the principal.
I have three tables as shown below:
and I want to get the columns from all three, plus a count of the number of episodes in each series and to get a result like this:
Currently, I am opening multiple DB threads and I am afraid that as I get more visitors on my site it will eventually respond really slowly.
Any ideas?
Thanks a lot!

Answer 1

First join all the tables together to get the columns. Then, to get a count, use a window function:
SELECT count(*) over (partition by seriesID) as NumEpisodesInSeries,
st.SeriesId, st.SeriesName, et.episodeID, et.episodeName,
ct.createdID, ct.CreatorName
FROM series_table st join
episode_table et
ON et.ofSeries = st.seriesID join
creator_table ct
ON ct.creatorID = st.byCreator;

Answer 2

Do your appropriate joins between the tables and their IDs as you would expect, and also join onto the result of a subquery that determines the total episode count using the Episodes table.
SELECT SeriesCount.NumEpisodes AS #OfEpisodesInSeries,
S.id AS SeriesId,
S.name AS SeriesName,
E.id AS EpisodeId,
E.name AS EpisodeName,
C.id AS CreatorId,
C.name AS CreatorName
FROM
Series S
INNER JOIN
Episodes E
ON E.seriesId = S.id
INNER JOIN
Creators C
ON S.creatorId = C.id
INNER JOIN
(
SELECT seriesId, COUNT(id) AS NumEpisodes
FROM Episodes
GROUP BY seriesId
) SeriesCount
ON SeriesCount.seriesId = S.id
SQL Fiddle Schema:
CREATE TABLE Series (id int, name varchar(20), creatorId int)
INSERT INTO Series VALUES(1, 'Friends', 1)
INSERT INTO Series VALUES(2, 'Family Guy', 2)
INSERT INTO Series VALUES(3, 'The Tonight Show', 1)
CREATE TABLE Episodes (id int, name varchar(20), seriesId int)
INSERT INTO Episodes VALUES(1, 'Joey', 1)
INSERT INTO Episodes VALUES(2, 'Ross', 1)
INSERT INTO Episodes VALUES(3, 'Phoebe', 1)
INSERT INTO Episodes VALUES(4, 'Stewie', 2)
INSERT INTO Episodes VALUES(5, 'Kevin Kostner', 3)
INSERT INTO Episodes VALUES(6, 'Brad Pitt', 3)
INSERT INTO Episodes VALUES(7, 'Tom Hanks', 3)
INSERT INTO Episodes VALUES(8, 'Morgan Freeman', 3)
CREATE TABLE Creators (id int, name varchar(20))
INSERT INTO Creators VALUES(1, 'Some Guy')
INSERT INTO Creators VALUES(2, 'Seth McFarlane')

Answer 3

Try this:
http://www.sqlfiddle.com/#!3/5f938/17
select min(ec.num) as NumEpisodes,s.Id,S.Name,
Ep.ID as EpisodeID,Ep.name as EpisodeName,
C.ID as CreatorID,C.Name as CreatorName
from Episodes ep
join Series s on s.Id=ep.SeriesID
join Creators c on c.Id=s.CreatorID
join (select seriesId,count(*) as Num from Episodes
group by seriesId) ec on s.id=ec.seriesID
group by s.Id,S.Name,Ep.ID,Ep.name,C.ID,C.Name
Thanks Gordon

Answer 4

I would do the following:
SELECT (SELECT Count(*)
FROM episodetbl e1
WHERE e1.ofseries = s.seriesid) AS "#ofEpisodesInSeries",
s.seriesid,
s.seriesname,
e.episodeid,
e.episodename,
c.creatorid,
c.creatorname
FROM seriestbl s
INNER JOIN creatortbl c
ON s.bycreator = c.creatorid
INNER JOIN episodetbl e
ON e.ofseries = s.seriesid