I had the following query that doesn't work and I was wondering how to fix it.
Player.select("players.*,
(SELECT COUNT(*) FROM Results
WHERE results.player_id = players.id and win = true)
as wins").where("wins > 0").order("wins desc")
I'm trying to limit parent Player records by a count of how many times its foreign key appears in the Results table when the boolean win is set to true. However, sometimes the foreign key will appear in the Results table but the boolean win field will be false resulting in a count of zero for records that I don't want to see, so I thought I would try and eliminate these count of zero records using the .where("wins > 0") clause but I get this error:
PGError: ERROR: column "wins" does not exist
The funny thing is it finds the wins field when I try and order by it, but not with the added where clause.
I believe the following query will work:
select players.*, count(results.id) as wins from players left join results on results.player_id = players.id and results.win = true group by players.id having count(results.id) > 0 order by wins desc;
This should Railsify thus, though naturally I haven't tested it:
Player.select('players.*, count(results.id) as wins').joins('left join results on results.player_id = players.id and results.win = true').group('players.id').having('count(results.id) > 0').order('wins desc')
If you don't care about rows where wins = 0, you can do an inner join instead of a left join, which might be faster.
Related
I have the following data in table VehiclesAccSummary:
I am not sure how to do this but what I want is a query that would return all rows where there where only two car in the accident and it was a head on crash so in both cars PointOfImpact was 'Front' i know in need to do some inner join on the same table but i don' want to join same car with it self. Any idea ?
The end result should be something like this
You can use a subquery to count the number of "Front' records for each AccRef.
SELECT *
FROM VehiclesAccSummary INNER JOIN
(SELECT VehiclesAccSummary.AccRef, Count(VehiclesAccSummary.PointOfImpact) AS CountOfPointOfImpact FROM VehiclesAccSummary GROUP BY VehiclesAccSummary.AccRef, VehiclesAccSummary.PointOfImpact HAVING VehiclesAccSummary.PointOfImpact="Front") AS FrontCount
ON VehiclesAccSummary.AccRef = FrontCount.AccRef
WHERE VehiclesAccSummary.NumCars = 2 AND CountOfPointOfImpact = 2;
This will limit the records to AccRefs with NumCar = 2 and the count of Front records = 2.
Edit: Since the same car can be listed in multiple records, we need a new approach. Try this:
SELECT VehiclesAccSummary.*, Subquery.CountOfPointOfImpact
FROM VehiclesAccSummary LEFT JOIN (SELECT VehiclesAccSummary.AccRef, Count(VehiclesAccSummary.PointOfImpact) AS CountOfPointOfImpact
FROM VehiclesAccSummary
WHERE (((VehiclesAccSummary.PointOfImpact)<>"Front"))
GROUP BY VehiclesAccSummary.AccRef) AS Subquery ON VehiclesAccSummary.AccRef = Subquery.AccRef
WHERE (((Subquery.CountOfPointOfImpact) Is Null));
Instead of confirming that the count of front accidents is 2, this confirms that the count of non-front accidents is 0.
Find all teams that only won 1 game in tourney #3 (1 column, 4 rows)
My thought process to create this query is that I need to count (WonGame)s for each Team. And that that number cannot be has to equal 1. But When I run my query I get no results (I should get 4 teams).
Experimenting with my query I changed the equals to a greater than and that returned 8 results. So I don't understand why equals 1 returns no results.
Also I checked my Data and there is indeed 4 teams that one only one game during Tournament #3.
select Teams.TeamName
from Teams
join Bowlers on Teams.TeamID = Bowlers.TeamID
join Bowler_Scores on Bowlers.BowlerID = Bowler_Scores.BowlerID
join Match_Games on Bowler_Scores.GameNumber = Match_Games.GameNumber
join Tourney_Matches on Match_Games.MatchID = Tourney_Matches.MatchID
where Tourney_Matches.TourneyID = 3
group by Teams.TeamName
having count(Bowler_Scores.WonGame) = 1;
Bowling League DB Structure
Bowling League Data
The diagram seems to indicate that the relationship between Match_Games and Bowler_Scores is on BOTH of MatchID and GameNumber
If you change your JOIN conditions to be both columns
join Match_Games on Bowler_Scores.GameNumber = Match_Games.GameNumber and Bowler_Scores.MatchID = Match_Games.MatchID
Then you might get the required answer.
I can only speculate on what your data really looks like. However, it is doubtful that this expression:
having count(Bowler_Scores.WonGame) = 1;
does what you want. This counts the number of non-NULL values. Presumably, WonGame as some value such as "1" or "W" for the winner. If the value were 1, then the correct expression would be:
having sum(Bowler_Scores.WonGame) = 1
This is just speculation though without a better description of your data.
EDIT:
Based on the comment:
having sum(convert(int, Bowler_Scores.WonGame)) = 1
So I got this query:
Data structure:
Users
id---inlog----name----more stuff
llntoets
id---code----inlog----more stuff
oefeningen
id---speler---status----morestuff
(inlog and speler are always the same values for a user)
SELECT
// Some other stuff working
SUM(o.status) AS oefn
FROM users AS u
LEFT JOIN llntoets AS l
ON (u.inlog = l.inlog)
LEFT JOIN oefeningen AS o
ON (u.inlog = o.speler) AND o.status = 'afgewerkt'
WHERE
code = '$code'
GROUP BY l.inlog
ORDER BY klas ASC, klasnr ASC
Everything runs fine except 1 thing the oefn variable. It shows a number sometimes it shows the correct value and sometimes it shows a value that is much higher than it should be. Someone told me it could be because of the GROUP BY. Can someone help me pls?
It is supposed to count the total records from table oefeningen where status = 'afgewerkt' and where the speler is the inlog from users. Thanks, if you got other questions ask will try to explain more.
the SUM(o.status) in your query it is not supposed to count the total records of table oefeningen.
that sum is the sum of the values of all the joined rows that satisfy your criteria that can be a much higher number.
also note that applying the filter o.status = 'afgewerkt' you are performing a JOIN even if you wrote LEFT JOIN throghout the query.
A very simple issue as it appears but somehow not working for me on Oracle 10gXE.
Based on my SQLFiddle, I have to show all staff names and count if present or 0 if no record found having status = 2
How can I achieve it in a single query without calling Loop in my application side.
SELECT S.NAME,ISTATUS.STATUS,COUNT(ISTATUS.Q_ID) as TOTAL
FROM STAFF S
LEFT OUTER JOIN QUESTION_STATUS ISTATUS
ON S.ID = ISTATUS.DONE_BY
AND ISTATUS.STATUS = 2 <--- instead of WHERE
GROUP BY S.NAME,ISTATUS.STATUS
By filtering in the WHERE clause, you filter too late, and you remove STAFF rows that you do want to see. Moving the filter into the join condition means only QUESTION_STATUS rows get filtered out.
Note that STATUS is not really a useful column here, since you won't ever get any result other than 2 or NULL, so you could omit it:
SELECT S.NAME,COUNT(ISTATUS.Q_ID) as TOTAL
FROM STAFF S
LEFT OUTER JOIN QUESTION_STATUS ISTATUS
ON S.ID = ISTATUS.DONE_BY
AND ISTATUS.STATUS = 2
GROUP BY S.NAME
I corrected your sqlfiddle: http://sqlfiddle.com/#!4/90ba0/12
The rule of thumb is that the filters must appear in the ON condition of the table they depend on.
Move filter into the LEFT JOIN , also use COALESCE to have your results display 0 instead of null as you requested in your question
select S.NAME,COALESCE(ISTATUS.STATUS,0),COUNT(ISTATUS.Q_ID) as TOTAL
from STAFF S
LEFT OUTER JOIN QUESTION_STATUS ISTATUS
ON S.ID = ISTATUS.DONE_BY
AND ISTATUS.STATUS =2
GROUP BY S.NAME,ISTATUS.STATUS
I am putting together a nice little database for adding values to options, all these are setup through a map (Has and Belongs to Many) table, because many options are pointing to a single value.
So I am trying to specify 3 option.ids and a single id in a value table - four integers to point to a single value. Three tables. And I am running into a problem with the WHERE part of the statement, because if multiple values share an option there are many results. And I need just a single result.
SELECT value.id, value.name FROM value
LEFT JOIN (option_map_value, option_table)
ON (value.id = option_map_value.value_id AND option_map_value.option_table_id = option_table.id)
WHERE option_table.id IN (5, 2, 3) AND value.y_axis_id = 16;
The problem with the statement seems to be the IN on the WHERE clause. If one of the numbers are different in the IN() part, then there are multiple results - which is not good.
I have tried DISTINCT, which again works if there is one result, but returns many if there is many. The closest we have gotten to is adding a count - to return to value with the most options at the top.
So is there a way to do the WHERE to be more specific. I cannot break it out into option_table.id = 5 AND option_table.id = 2 - because that one fails. But can the WHERE clause be more specifc?
Maybe it is me being pedantic, but I would like to be able to return just the single result, instead of a count of results... Any ideas?
The problem with the statement seems to be the IN on the WHERE clause. If one of the numbers are different in the IN() part, then there are multiple results - which is not good. I have tried DISTINCT, which again works if there is one result, but returns many if there is many. The closest we have gotten to is adding a count - to return to value with the most options at the top.
You were very close, considering the DISTINCT:
SELECT v.id,
v.name
FROM VALUE v
LEFT JOIN OPTION_MAP_VALUE omv ON omv.value_id = v.id
LEFT JOIN OPTION_TABLE ot ON ot.id = omv.option_table_id
WHERE ot.id IN (5, 2, 3)
AND v.y_axis_id = 16
GROUP BY v.id, v.name
HAVING COUNT(*) = 3
You were on the right track, but needed to use GROUP BY instead in order to be able to use the HAVING clause to count the DISTINCT list of values.
Caveat emptor:
The GROUP BY/HAVING COUNT version of the query is dependent on your data model having a composite key, unique or primary, defined for the two columns involved (value_id and option_table_id). If this is not in place, the database will not stop duplicates being added. If duplicate rows are possible in the data, this version can return false positives because a value_id could have 3 associations to the option_table_id 5 - which would satisfy the HAVING COUNT(*) = 3.
Using JOINs:
A safer, though more involved, approach is to join onto the table that can have multiple options, as often as you have criteria:
SELECT v.id,
v.name
FROM VALUE v
JOIN OPTION_MAP_VALUE omv ON omv.value_id = v.id
JOIN OPTION_TABLE ot5 ON ot5.id = omv.option_table_id
AND ot5.id = 5
JOIN OPTION_TABLE ot2 ON ot2.id = omv.option_table_id
AND ot2.id = 2
JOIN OPTION_TABLE ot3 ON ot3.id = omv.option_table_id
AND ot3.id = 3
WHERE v.y_axis_id = 16
GROUP BY v.id, v.name