Please find the Table " MarkCompare" below
SEMESTER - PAPER - TEACHER 1 - TEACHER 2
1 - ENG - PASS - PASS
1 - MATH - PASS - FAIL
2 - ENG - PASS - FAIL
2 - MATH - FAIL - FAIL
I want to calculate a logic like below
No.Of.Times where both teachers gave same result / sum of occurences where first teacher both the teachers result differed
I am writing a query like this
select count(*) from MarkCompare where teacher1=teacher2 where paper='ENG' / (select count(*) from MarkCompare where teacher1<>teacher2 where paper='ENG')
select count(*) from MarkCompare where teacher1=teacher2 where paper='MATH' / (select count(*) from MarkCompare where teacher1<>teacher2 where paper='MATH')
Now, in future the number of papers may increase or decrease... I am unable to find a dynamic query to run for any number of papers.
Is there a way to do this without any procedure/function, just with a query
You can use a GROUP BY clause to aggregate the results for each paper listed in the table.
SELECT paper,
SUM(CASE WHEN teacher1 = teacher2 THEN 1 ELSE 0 END) AS AgreeCount,
SUM(CASE WHEN teacher1 <> teacher2 THEN 1 ELSE 0 END) AS DisagreeCount
FROM MarkCompare
GROUP BY paper;
Related
My very first question as a newb in SQL.
I want to count unique values from one column Transport, group them by ID and delete double values in the Transport column that may be caused by Product column. Could be very simple, but at this point I need another point of view.
This is the data
ID
Product
Transport
1
A
Plane
1
B
Plane
2
A
Train
2
B
Train
2
C
Ship
3
A
Plane
3
B
Train
3
C
Ship
3
D
Ship
I would want to have the ID as unique values and then count each of the unique values of the Transport. If I do it with a normal GROUP BY, the Products will double the counting.
The result I need has to count each of the Transport values in separated columns without being doubled by the Product column. So it should look something like:
ID
Plane
Train
Ship
1
1
0
0
2
0
1
1
3
1
1
1
I think it's simple but maybe I'm missing something. Any help would be appreciated!
Thank you.
You can get a pivot by combining CASE with MAX(), as in:
select
id,
max(case when transport = 'Plane' then 1 else 0 end) as plance,
max(case when transport = 'Train' then 1 else 0 end) as train,
max(case when transport = 'Ship' then 1 else 0 end) as ship
from t
group by id
Just adding something to #The Impater's result
SELECT
id,
MAX(transport = 'Plane') AS plance,
MAX(transport = 'Train') AS train,
MAX(transport = 'Ship') AS ship
FROM `test_table`
GROUP BY id
I was taught there is no need to assign 1 and 0 when it can be done via boolean-type logic as results are returned either in 0 or 1.
I have a database with roughly 6 million entries - and will grow - where I'm running queries to return for a HighCharts charting functionality. I need to read longitudinally over years, so I'm running queries like this:
foreach($states as $state_id) { //php code
SELECT //mysql psuedocode
sum(case when mydatabase.Year = '2003' then 1 else 0 end) Year_2003,
sum(case when mydatabase.Year = '2004' then 1 else 0 end) Year_2004,
sum(case when mydatabase.Year = '2005' then 1 else 0 end) Year_2005,
sum(case when mydatabase.Year = '2006' then 1 else 0 end) Year_2006,
sum(case when mydatabase.Year = '2007' then 1 else 0 end) Year_2007,
sum(case when mydatabase.Year = '$more_years' then 1 else 0 end) Year_$whatever_year,
FROM mytable
WHERE State='$state_id'
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
AND "other_filters IN (etc, etc, etc)
} //end php code
But for various state at once... So returning lets say 5 states, each with the above statement but a state ID is substituted. Meanwhile the years can be any number of years, the Sex (male/female/other) and Age segment and other modifiers keep changing based on filters. The queries are long (at minimum 30-40seconds) a piece. So a thought I had - unless I'm totally doing it wrong - is to actually store the above query in a second table with the results, and first check that "meta query" and see if it was "cached" and then return the results without reading the db (which won't be updated very often).
Is this a good method or are there potential problems I'm not seeing?
EDIT: changed to table, not db (duh).
Table structure is:
id | Year | Sex | Age_segment | Another_filter | Etc
Nothing more complicated than that and no joining anything else. There are keys on id, Year, Sex, and Age_segment right now.
Proper indexing is what is needed to speed up the query. Start by doing an "EXPLAIN" on the query and post the results here.
I would suggest the following to start off. This way avoids the for loop and returns the data in 1 query. Not knowing the number of rows and cardinality of each column I suggest a composite index on State and Year.
SELECT mytable.State,mytable.Year,count(*)
FROM mytable
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
AND "other_filters IN (etc, etc, etc)
GROUP BY mytable.State,mytable.Year
The above query can be further optimised by checking the cardinality of some of the columns. Run the following to get the cardinality:
SELECT Age_segment FROM mytable GROUP BY Age_segment;
Pseudo code...
SELECT Year
, COUNT(*) total
FROM my_its_not_a_database_its_a_table
WHERE State = $state_id
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
GROUP
BY Year;
I'm trying to make a report in SSRS where I show some totals from the same table. I know I can use selects into select, but I've heard that could affect the performance and make it slow. That is why I decided to use store procedures but I'm not so familiar with it (I only did some basic SP) so some help will be apreciated:
This is what I need to get:
|--------------|------------------------- TOTALS AND PERCENTAGES ----------------------|
|COMPANY | PACKAGES | WEIGHT | PACKAGE_DELIVERED |% DELIVERED | ONTIME |% ONTIME |
These are the querys I did in a previous version of the report (using asp):
SELECT COMPANY_NAME, COUNT(ID) AS PACKAGES, SUM(WEIGHT) AS WEIGHT
FROM PACKAGE
WHERE ACTUAL_DELIVERY_DATE BETWEEN 'X' AND 'Y'
GROUP BY COMPANY_CODE, COMPANY_NAME
Then I put the results in arrays and then make a new select to get the rest of information adding the COMPANY as filter:
SELECT COMPANY_CODE, ESTIMATED_DELIVERY_DATE, ACTUAL_DELIVERY_DATE
FROM PACKAGE
WHERE ACTUAL_DELIVERY_DATE BETWEEN 'X' AND 'Y'
AND STATUS = 'DELIVERED'
AND COMPANY_CODE = 'DHL'
ORDER BY STATUS
For every row
PACKAGES_DELIVERED = + 1
IF ACTUAL_DELIVERY_DATE < ESTIMATED_DELIVERY_DATE THEN ONTIME = + 1
Next
Then I calculate the percentages and show all together in a table.
Somebody that can help me to put all this in a Store Procedure or maybe have another idea.
Thanks in advance.
I would add the following columns to the original SELECT, using SUM on a CASE statement:
, SUM ( CASE WHEN STATUS = 'DELIVERED' THEN 1 ELSE 0 END ) AS PACKAGES_DELIVERED
, SUM ( CASE WHEN STATUS = 'DELIVERED' AND ACTUAL_DELIVERY_DATE < ESTIMATED_DELIVERY_DATE THEN 1 ELSE 0 END ) AS ONTIME
This doesnt seem complex enough to bother with a Stored Procedure.
I have a MySQL table like this:
ID - Time - Value
And I'm getting every pair of ID, Time (grouped by ID) where Value is greater than a certain threshold. So basicaly, I'm getting every ID which has at least one time a value greater than the threshold. The query looks like this:
SELECT ID, Time FROM mydb.MYTABLE
WHERE Value>%s AND Time>=%s AND Time<=%s
GROUP BY ID
EDIT: The Time checks allow to operate in a time range of my choice between all the data which is into the table; it has nothing else to do with what I am asking.
It works perfectly, but now I want to add some filtering: I want it to avoid those times the value is greater than the threshold (let's call it alarms) if the alarm hasn't happened also the Time just before or just after. I mean: if the alarm accurs at a single, isolated instant of time instead of two consecutive instants of time, I'll consider it is a false alarm and avoid it to be returned at the query response.
Of course I can do this with a call for each Id to check for this, but I'd like to do this in a single query to make it faster. I guess I could use conditionals, but I don't have that expertise at MySQL.
Any help?
EDIT2: Example for Threshold = 10
ID - Time - Value
1 - 2004 - 9
1 - 2005 - 11
1 - 2006 - 8
2 - 2107 - 12
2 - 2109 - 13
3 - 3402 - 11
3 - 3403 - 12
In this example, only ID 3 should be a valid alarm, since 2 consecutive time values for this ID have their value > threshold. ID 1 has a single, isolated alarm, so it should be filteres. For ID 2 there are 2 alarms, but not consecutive, so it should be also filtered.
Something like this:
10 - is a threshold
0 - minimum of the time period
100000 - maximum of the time period
select ID, min(Time)
from
(
SELECT ID, Time,
(select max(time) from t
where Time<t1.Time
and Id=t1.Id
and Value>10) LAG_G,
(select max(time) from t
where Time<t1.Time
and Id=t1.Id
and Value<=10) LAG_L,
(select min(time) from t
where Time>t1.Time
and Id=t1.Id
and Value>10) LEAD_G,
(select min(time) from t
where Time>t1.Time
and Id=t1.Id
and Value<=10) LEAD_L
FROM t as t1
WHERE Value>10 AND Time>=0 AND Time<=100000
) t3
where ifnull(LAG_G,0)>ifnull(LAG_L,0)
OR
ifnull(LEAD_G,100000)<ifnull(LEAD_L,100000)
GROUP BY ID
SQLFiddle demo
This query works for searching near records.
If you need to search records by Time (+1, -1 ) as you've mentioned in the comment try this query:
select ID, min(Time) from t as t1
where Value>10
AND Time>=%s2 AND Time<=%s1
and
(
Exists(select 1 from t where Value>10
and Id=t1.Id
and Time=t1.Time-1)
OR
Exists(select 1 from t where Value>10
and Id=t1.Id
and Time=t1.Time+1)
)
group by ID
SQLFiddle demo
such alarm ?
SELECT ID, Time , count(if(value>%treshold ,1,0)) alert_active
FROM mydb.MYTABLE
WHERE Value>%s3 AND Time>=%s2 AND Time<=%s1
GROUP BY ID;
i don't understand exactly:
In this example, only ID 3 should be a valid alarm, since 2
consecutive time values for this ID have their value > threshold. ID 1
has a single, isolated alarm, so it should be filteres. For ID 2 there
are 2 alarms, but not consecutive, so it should be also filtered.
I guess that You want filter alerts:
SELECT ID, Time
FROM mydb.MYTABLE
WHERE Value>%s3 AND Time>=%s2 AND Time<=%s1
GROUP BY ID
having value<%treshold;
What's the best way to compare two queries by two columns? these are my tables:
This table shows exam questions
idEvaluation | Question | AllowMChoice | CorrectAnswer|
1 1 0 3
1 2 1 4
1 2 1 5
1 3 0 9
This table shows a completed exam
idExam| idEvaluation | Question | ChosenAnswer|
25 1 1 2
25 1 2 4
25 1 2 5
25 1 3 8
I have to calculate the percentage of correct Answers, considering to certain questions may allow multiple selection.
Correct Answers / Total Answers * 100
thanks for your tips!
This code will show you a listing of Questions and whether or not they were answered correctly.
select
A.Question,
min(1) as QuestionsCount,
-- if this evaluates to null, they got A) the answer wrong or B) this portion of the answer wrong
-- we use MIN() here because we want to mark multi-answer questions as wrong if any part of the answer is wrong.
min(case when Q.idEvaluation IS NULL then 0 else 1 end) as QuestionsCorrect
from
ExamAnswers as A
left join ExamQuestions as Q on Q.Question = A.Question and Q.CorrectAnswer = A.ChosenAnswer
group by
A.Question -- We group by question to merge multi-answer-questions into 1
Output Confirmed:
Note, the columns are intentionally named this way, as they are to be included as a subquery in part-2 below.
This code will give you the test score.
select
sum(I.QuestionsCorrect) as AnswersCorrect,
sum(I.QuestionsCount) as QuestionTotal,
convert(float,sum(I.QuestionsCorrect)) / sum(I.QuestionsCount) as PercentCorrect -- Note, not sure of the cast-to-float syntax for MySQL
from
(select
A.Eval,
A.Question,
min(1) as QuestionsCount,
min(case when Q.idEvaluation IS NULL then 0 else 1 end) as QuestionsCorrect
from
ExamAnswers as A
left join ExamQuestions as Q on Q.Question = A.Question and Q.CorrectAnswer = A.ChosenAnswer
where
A.Eval = 25
group by
A.Question, A.Eval) as I
group by
I.Eval
Output Confirmed:
This will communicate the general concept. Your column names idEvaluation and Eval are difficult for me to understand, but I'm sure you can adjust the code above to suit your purposes.
Note, I did this in sql server, but I used fairly basic SQL functionality, so it should translate to MySQL well.