I got stuck with a tricky query (in MS Access 2013). I'd like to do a fairly simple Thing:
I have got two Tables (see example below): Table "scores" with scores of an exam and table "grading_key".
The scores table has a field named "quotient" which contains a float value representing the percentage of success (1.0 being all questions answered correctly). The grading_key table has quotient limits which separate one grade level from the next. Thus the “grading_key” table can be used to get a grade for any quotient value.
A grade can be found by performing:
SELECT TOP 1 Grade FROM grading_key WHERE {ANY_QUOTIENT_VALUE} <= Quotient
Sample Tables:
|-grade_key-| |-----scores-----|
Quotient Grade StudentId Quotient
0,92 1 123 0,85
0,87 1,5 321 0,8
0,81 2 766 0,91
0,76 2,5 222 0,78
My Problem is, I’d like to join scores and grades in a query resulting in associating each quotient in table “scores” with one grade in table “grade_key” (see desired_result below). Unfortunately I can’t simply join, as the quotients in “scores” do not necessarily match the grade limits defined in “grade_key”.
Currently I used a VBA function (calculateScoreForQuotient()) but I want to remove the VBA dependency as the resulting table should be called from outside MS Access and in this case VBA functions do not work.
|--------Desired_Result-------|
StudentId Quotient Grade
123 0,85 2
312 0,8 2,5
Does anyone know a way to get desired table with plain SQL? I played around with different combinations of JOINs and and WHEREs for quite a while now but my best result was to associate all available grades with each student (not really meaningful).
Any help would safe my day ;-)
You can use a co-related sub-query to return the grade based on the quotient of the student. You could use Max() or TOP 1 with an order by clause, whichever you prefer.
select
StudentID,
Quotient,
(select Max(grade) from Grades where grades.quotient <= student.quotient) as grade
from Student
Related
Is there any way of joining the result of a case statement with a reference table without creating a CTE, ect.
Result AFTER CASE statement:
ID Name Bonus Level (this is the result of a CASE statement)
01 John A
02 Jim B
01 John B
03 Jake C
Reference table
A 10%
B 20%
C 30%
I want to then get the % next to each employee, then the max %age using the MAX function and grouping by ID, then link it back again to the reference so that each employee has the single correct (highest) bonus level next to their name. (This is a totally fictitious scenario, but very similar to what I am looking for).
Just need help with joining the result of the CASE statement with the reference table.
Thanks in advance.
In place of a temporary value as the result of the case statement, you could use a select statement from the reference table.
So if your case statement looks like:
case when variable1=value then bonuslevel =A
Then, replacing it like this might help
case when variable1=value then (select percentage from ReferenceTable where variable2InReferenceTable=A)
Don't know if I am overly simplifying, but based on the results of your case result query, why not just join that to the reference table, and do a max grouped by ID/Name. Since the ID and persons name wont change anyhow since they are the same person, you are just getting the max you want. To complete the Bonus level, rejoin just that portion after the max percentage determined for the person.
select
lvl1.ID,
lvl1.Name,
lvl1.FinalBonus,
rt2.BonusLvl
from
( select
PQ.ID,
PQ.Name,
max( rt.PcntBonus ) as FinalBonus
from
(however you
got your
data query ) PQ
JOIN RefTbl rt
on PQ.BonusLvl = rt.BonusLvl
) lvl1
JOIN RefTbl rt2
on lvl1.FinalBonus = rt2.PcntBonus
Since the Bonus levels (A,B,C) do not guarantee corresponding % levels (10,20,30), I did it this way... OTHERWISE, you could have just used max() on both the bonus level and percent. But what if your bonus levels were listed as something like
Limited 10%
Aggressive 20%
Ace 30%
You could see that a max of the level above would have "Limited", but the max % = 30 is associated with an "Ace" sales rep... Get the 30% first, then see what the label that matched that is.
What I am trying to do is fairly simple. I just want to add a row number to a query. Since this is in Access is a bit more difficult than other SQL, but under normal circumstances is still doable using solutions such as DCount or Select Count(*), example here: How to show row number in Access query like ROW_NUMBER in SQL or Access SQL how to make an increment in SELECT query
My Issue
My issue is I'm trying to add this counter to a multi-join query that orders by fields from numerous tables.
Troubleshooting
My code is a bit ridiculous (19 fields, seven of which are long expressions, from 9 different joined tables, and ordered by fields from 5 of those tables). To make things simple, I have an simplified example query below:
Example Query
SELECT DCount("*","Requests_T","[Requests_T].[RequestID]<=" & [Requests_T].[RequestID]) AS counter, Requests_T.RequestHardDeadline AS Deadline, Requests_T.RequestOverridePriority AS Priority, Requests_T.RequestUserGroup AS [User Group], Requests_T.RequestNbrUsers AS [Nbr of Users], Requests_T.RequestSubmissionDate AS [Submitted on], Requests_T.RequestID
FROM (((((((Requests_T
INNER JOIN ENUM_UserGroups_T ON ENUM_UserGroups_T.UserGroups = Requests_T.RequestUserGroup)
INNER JOIN ENUM_RequestNbrUsers_T ON ENUM_RequestNbrUsers_T.NbrUsers = Requests_T.RequestNbrUsers)
INNER JOIN ENUM_RequestPriority_T ON ENUM_RequestPriority_T.Priority = Requests_T.RequestOverridePriority)
ORDER BY Requests_T.RequestHardDeadline, ENUM_RequestPriority_T.DisplayOrder DESC , ENUM_UserGroups_T.DisplayOrder, ENUM_RequestNbrUsers_T.DisplayOrder DESC , Requests_T.RequestSubmissionDate;
If the code above is trying to select a field from a table not included, I apologize - just trust the field comes from somewhere (lol i.e. one of the other joins I excluded to simply the query). A great example of this is the .DisplayOrder fields used in the ORDER BY expression. These are fields from a table that simply determines the "priority" of an enum. Example: Requests_T.RequestOverridePriority displays to the user as an combobox option of "Low", "Med", "High". So in a table, I assign a numerical priority to these of "1", "2", and "3" to these options, respectively. Thus when ENUM_RequestPriority_T.DisplayOrder DESC is called in order by, all "High" priority requests will display above "Medium" and "Low". Same holds true for ENUM_UserGroups_T.DisplayOrder and ENUM_RequestNbrUsers_T.DisplayOrder.
I'd also prefer to NOT use DCOUNT due to efficiency, and rather do something like:
select count(*) from Requests_T where Requests_T.RequestID>=RequestID) as counter
Due to the "Order By" expression however, my 'counter' doesn't actually count my resulting rows sequentially since both of my examples are tied to the RequestID.
Example Results
Based on my actual query results, I've made an example result of the query above.
Counter Deadline Priority User_Group Nbr_of_Users Submitted_on RequestID
5 12/01/2016 High IT 2-4 01/01/2016 5
7 01/01/2017 Low IT 2-4 05/06/2016 8
10 Med IT 2-4 07/13/2016 11
15 Low IT 10+ 01/01/2016 16
8 Low IT 2-4 01/01/2016 9
2 Low IT 2-4 05/05/2016 2
The query is displaying my results in the proper order (those with the nearest deadline at the top, then those with the highest priority, then user group, then # of users, and finally, if all else is equal, it is sorted by submission date). However, my "Counter" values are completely wrong! The counter field should simply intriment +1 for each new row. Thus if displaying a single request on a form for a user, I could say
"You are number: Counter [associated to RequestID] in the
development queue."
Meanwhile my results:
Aren't sequential (notice the first four display sequentially, but then the final two rows don't)! Even though the final two rows are lower in priority than the records above them, they ended up with a lower Counter value simply because they had the lower RequestID.
They don't start at "1" and increment +1 for each new record.
Ideal Results
Thus my ideal result from above would be:
Counter Deadline Priority User_Group Nbr_of_Users Submitted_on RequestID
1 12/01/2016 High IT 2-4 01/01/2016 5
2 01/01/2017 Low IT 2-4 05/06/2016 8
3 Med IT 2-4 07/13/2016 11
4 Low IT 10+ 01/01/2016 16
5 Low IT 2-4 01/01/2016 9
6 Low IT 2-4 05/05/2016 2
I'm spoiled by PLSQL and other software where this would be automatic lol. This is driving me crazy! Any help would be greatly appreciated.
FYI - I'd prefer an SQL option over VBA if possible. VBA is very much welcomed and will definitely get an up vote and my huge thanks if it works, but I'd like to mark an SQL option as the answer.
Unfortuantely, MS Access doesn't have the very useful ROW_NUMBER() function like other clients do. So we are left to improvise.
Because your query is so complicated and MS Access does not support common table expressions, I recommend you follow a two step process. First, name that query you already wrote IntermediateQuery. Then, write a second query called FinalQuery that does the following:
SELECT i1.field_primarykey, i1.field2, ... , i1.field_x,
(SELECT field_primarykey FROM IntermediateQuery i2
WHERE t2.field_primarykey <= t1.field_primarykey) AS Counter
FROM IntermediateQuery i1
ORDER BY Counter
The unfortunate side effect of this is the more data your table returns, the longer it will take for the inline subquery to calculate. However, this is the only way you'll get your row numbers. It does depend on having a primary key in the table. In this particular case, it doesn't have to be an explicitly defined primary key, it just needs to be a field or combination of fields that is completely unique for each record.
I've looked into Dynamic SQL and the inc() function, but neither are really what I'm after.
Say I have a database like this:
grade name age
9 Bob 9
10 Sue 11
11 Larry 15
9 Joe 8
10 Carrot 10
I want to create a table that first selects all the rows with the lowest grade (9) then displays the oldest. It then goes through and searches for the next highest grade (10) and displays the oldest. Then goes to the next highest grade (11) and displays the oldest.
I'd like for them all to be in the same table and not have to write out a separate SQL call and different PHP variables for each grade.
This is the SQL call I have right now:
$query = "SELECT * FROM horses WHERE grade='1' ORDER BY points DESC LIMIT 1" or die(mysql_error());
Is there a way I can make the grade column increment until it reaches the highest number in the database?
Thanks for any suggestions.
You don't need a loop for this if I understand your request. Instead, you need a MAX() aggregate grouped by grade. The following method should work independently of your RDBMS. It relies on a JOIN against a subquery which returns the greatest age per group to get the age/group pair and join that back against the main table to retrieve the name (and other columns as needed).
SELECT
horses.grade,
horses.name,
horses.age
FROM
horses
JOIN (
SELECT grade, MAX(age) as maxage
FROM horses
GROUP BY grade
) ma ON horses.grade = ma.grade AND horses.age = ma.maxage
ORDER BY grade ASC
Here is an example on SQLFiddle.com
Returns:
GRADE NAME AGE
9 Bob 9
10 Sue 11
11 Larry 15
It is generally far faster an less resource-intensive to do one query instead of multiple queries in a loop, so this should be the approach whenever possible.
I'm somewhat new to SQL queries, and I'm struggling with this particular problem.
Let's say I have query that returns the following 3 records (kept to one column for simplicity):
Tom
Jack
Tom
And I want to have those results grouped by the name and also include the fraction (ratio) of the occurrence of that name out of the total records returned.
So, the desired result would be (as two columns):
Tom | 2/3
Jack | 1/3
How would I go about it? Determining the numerator is pretty easy (I can just use COUNT() and GROUP BY name), but I'm having trouble translating that into a ratio out of the total rows returned.
SELECT name, COUNT(name)/(SELECT COUNT(1) FROM names) FROM names GROUP BY name;
Since the denominator is fixed, the "ratio" is directly proportional to the numerator. Unless you really need to show the denominator, it'll be a lot easier to just use something like:
select name, count(*) from your_table_name
group by name
order by count(*) desc
and you'll get the right data in the right order, but the number that's shown will be the count instead of the ratio.
If you really want that denominator, you'd do a count(*) on a non-grouped version of the same select -- but depending on how long the select takes, that could be pretty slow.
I have the following table (highscores),
id gameid userid name score date
1 38 2345 A 100 2009-07-23 16:45:01
2 39 2345 A 500 2009-07-20 16:45:01
3 31 2345 A 100 2009-07-20 16:45:01
4 38 2345 A 200 2009-10-20 16:45:01
5 38 2345 A 50 2009-07-20 16:45:01
6 32 2345 A 120 2009-07-20 16:45:01
7 32 2345 A 100 2009-07-20 16:45:01
Now in the above structure, a user can play a game multiple times but I want to display the "Games Played" by a specific user. So in games played section I can't display multiple games. So the concept should be like if a user played a game 3 times then the game with highest score should be displayed out of all.
I want result data like:
id gameid userid name score date
2 39 2345 A 500 2009-07-20 16:45:01
3 31 2345 A 100 2009-07-20 16:45:01
4 38 2345 A 200 2009-10-20 16:45:01
6 32 2345 A 120 2009-07-20 16:45:01
I tried following query but its not giving me the correct result:
SELECT id,
gameid,
userid,
date,
MAX(score) AS score
FROM highscores
WHERE userid='2345'
GROUP BY gameid
Please tell me what will be the query for this?
Thanks
Requirement is a bit vague/confusing but would something like this satisfy the need ?
(purposely added various aggregates that may be of interest).
SELECT gameid,
MIN(date) AS FirstTime,
MAX(date) AS LastTime,
MAX(score) AS TOPscore.
COUNT(*) AS NbOfTimesPlayed
FROM highscores
WHERE userid='2345'
GROUP BY gameid
-- ORDER BY COUNT(*) DESC -- for ex. to have games played most at top
Edit: New question about adding the id column to the the SELECT list
The short answer is: "No, id cannot be added, not within this particular construct". (Read further to see why) However, if the intent is to have the id of the game with the highest score, the query can be modified, using a sub-query, to achieve that.
As explained by Alex M on this page, all the column names referenced in the SELECT list and which are not used in the context of an aggregate function (MAX, MIN, AVG, COUNT and the like), MUST be included in the ORDER BY clause. The reason for this rule of the SQL language is simply that in gathering the info for the results list, SQL may encounter multiple values for such an column (listed in SELECT but not GROUP BY) and would then not know how to deal with it; rather than doing anything -possibly useful but possibly silly as well- with these extra rows/values, SQL standard dictates a error message, so that the user can modify the query and express explicitly his/her goals.
In our specific case, we could add the id in the SELECT and also add it in the GROUP BY list, but in doing so the grouping upon which the aggregation takes place would be different: the results list would include as many rows as we have id + gameid combinations the aggregate values for each of this row would be based on only the records from the table where the id and the gameid have the corresponding values (assuming id is the PK in table, we'd get a single row per aggregation, making the MAX() and such quite meaningless).
The way to include the id (and possibly other columns) corresponding to the game with the top score, is with a sub-query. The idea is that the subquery selects the game with TOP score (within a given group by), and the main query's SELECTs any column of this rows, even when the fieds wasn't (couldn't be) in the sub-query's group-by construct. BTW, do give credit on this page to rexem for showing this type of query first.
SELECT H.id,
H.gameid,
H.userid,
H.name,
H.score,
H.date
FROM highscores H
JOIN (
SELECT M.gameid, hs.userid, MAX(hs.score) MaxScoreByGameUser
FROM highscores H2
GROUP BY H2.gameid, H2.userid
) AS M
ON M.gameid = H.gameid
AND M.userid = H.userid
AND M.MaxScoreByGameUser = H.score
WHERE H.userid='2345'
A few important remarks about the query above
Duplicates: if there the user played several games that reached the same hi-score, the query will produce that many rows.
GROUP BY of the sub-query may need to change for different uses of the query. If rather than searching for the game's hi-score on a per user basis, we wanted the absolute hi-score, we would need to exclude userid from the GROUP BY (that's why I named the alias of the MAX with a long, explicit name)
The userid = '2345' may be added in the [now absent] WHERE clause of the sub-query, for efficiency purposes (unless MySQL's optimizer is very smart, currently all hi-scores for all game+user combinations get calculated, whereby we only need these for user '2345'); down side duplication; solution; variables.
There are several ways to deal with the issues mentioned above, but these seem to be out of scope for a [now rather lenghty] explanation about the GROUP BY constructs.
Every field you have in your SELECT (when a GROUP BY clause is present) must be either one of the fields in the GROUP BY clause, or else a group function such as MAX, SUM, AVG, etc. In your code, userid is technically violating that but in a pretty harmless fashion (you could make your code technically SQL standard compliant with a GROUP BY gameid, userid); fields id and date are in more serious violation - there will be many ids and dates within one GROUP BY set, and you're not telling how to make a single value out of that set (MySQL picks a more-or-less random ones, stricter SQL engines might more helpfully give you an error).
I know you want the id and date corresponding to the maximum score for a given grouping, but that's not explicit in your code. You'll need a subselect or a self-join to make it explicit!
Use:
SELECT t.id,
t.gameid,
t.userid,
t.name,
t.score,
t.date
FROM HIGHSCORES t
JOIN (SELECT hs.gameid,
hs.userid,
MAX(hs.score) 'max_score'
FROM HIGHSCORES hs
GROUP BY hs.gameid, hs.userid) mhs ON mhs.gameid = t.gameid
AND mhs.userid = t.userid
AND mhs.max_score = t.score
WHERE t.userid = '2345'