I have a table similar to this (3 rows, 4 columns: id, name, gradeA, gradeB):
id name gradeA gradeB
------------------------------
1 David 59 78
2 Anna 66 92
3 David 22 89
I'm looking for a query that will give me 1 numeric property for the highest grade by in the whole table by condition.
for example:
What is the highest grade for any student named David?
The answer should be { maxGrade: 89 }
Note: grades are stored as varchar values and should be cast to numeric values for comparison
You need to combine max() with greatest()
select max(greatest(gradea::int, gradeb::int)) as max_grade
from the_table
where name = 'David';
If you need a JSON result (because you wrote: result should be {maxGrade: 89}), you can wrap that query and convert the row to JSON:
select to_jsonb(t)
from (
select max(greatest(gradea::int, gradeb::int)) as "maxGrade"
from the_table
where name = 'David'
) t;
I would recommend a lateral join:
select max(grade::int) as max_grade
from t cross join lateral
(values (gradea), (gradeb)) v(grade)
where name = 'David';
In particular, this works if any of the grades are NULL.
It can also easily be tweaked to get which grade is the maximum:
select v.*
from t cross join lateral
(values ('a', gradea), ('b', gradeb)) v(which, grade)
where name = 'David'
order by grade::int desc
limit 1
Try the below:
We shall achieve with GREATEST and MAX:
We can make use of GREATEST to return the large value between the columns grade A and grade B for every user record
And use MAX to return the maximum grade if more than user matches with the same name.
SELECT
MAX(GREATEST(gradeA::integer, gradeB::integer)) as maxGrade
FROM
"table_name"
WHERE
"table_name"."name" = 'David';
Related
This is a question on a test. I have a table with two columns. I want to pivot on one of them and output the other.
Table structure:
(Name varchar(10), Age int)
I need output with age values as columns and Names listed below each age value.
From searching, I only see examples where there is at least one other column that is used to "group by" for want of a better term. In other words, there is a common factor in each row of the output. My problem does not have this property.
I tried:
SELECT
[agevalue1], [agevalue2], [agevalue3], [agevalue4]
FROM
(SELECT Name, Age FROM MyClass) AS SourceTable
PIVOT
(MAX(Name)
FOR Age IN ([agevalue1], [agevalue2], [agevalue3], [agevalue4])
) AS PivotTable;
I specified agevalue* as a string, i.e. in quotes. I got the column headings alright but a row of NULLS below them.
P.S.: The solution does not need to use pivot but I couldn't think of an alternative approach.
Sample Data:
Name Age
Bob 11
Rick 25
Nina 30
Sam 11
Cora 16
Rachel 25
Desired output:
11 16 25 30
Bob Cora Rick Nina
Sam NULL Rachel NULL
Try this :
with tab as
(
Select 'A' Name, 10 Age union all
Select 'B',11 union all
Select 'c',10 union all
Select 'D',11 union all
Select 'E',11 union all
Select 'F',11
)
select distinct
Age
, stuff((
select ',' + g.Name
from tab g
where g.age = g1.age
order by g.age
for xml path('')
),1,1,'') as Names_With_Same_Age
from tab g1
group by g1.age,Name
To group these together in one row:
11 16 25 30
Bob Cora Rick Nina
and separate them from another set, like:
11 16 25 30
Sam NULL Rachel NULL
they must have something different between each row, since doing a MAX(Name) would get you only one Name for each Age.
This query creates a number that links a particular Age to a row number and then pivots the result. As you said, the PIVOT will group by all columns not referenced in the PIVOT function, so it will group by this row indexer, separating the values like you wanted.
;WITH IndexedClass AS
(
SELECT
M.Name,
M.Age,
-- The ordering will determine which person goes first for each Age
RowIndexer = ROW_NUMBER() OVER (PARTITION BY M.Age ORDER BY M.Name)
FROM
MyClass AS M
)
SELECT
P.[11],
P.[16],
P.[25],
P.[30]
FROM
IndexedClass AS I
PIVOT (
MAX(I.Name) FOR I.Age IN ([11], [16], [25], [30])
) AS P
I have the following table which contains ID's and UserId's.
ID UserID
1111 11
1111 300
1111 51
1122 11
1122 22
1122 3333
1122 45
I'm trying to count the distinct number of 'IDs' so that I get a total, but I also need to get a total of ID's that have also seen the that particular ID as well... To get the ID's, I've had to perform a subquery within another table to get ID's, I then pass this into the main query... Now I just want the results to be displayed as follows.
So I get a Total No for ID and a Total Number for Users ID - Also would like to add another column to get average as well for each ID
TotalID Total_UserID Average
2 7 3.5
If Possible I would also like to get an average as well, but not sure how to calculate that. So I would need to count all the 'UserID's for an ID add them altogether and then find the AVG. (Any Advice on that caluclation would be appreciated.)
Current Query.
SELECT DISTINCT(a.ID)
,COUNT(b.UserID)
FROM a
INNER JOIN b ON someID = someID
WHERE a.ID IN ( SELECT ID FROM c WHERE GROUPID = 9999)
GROUP BY a.ID
Which then Lists all the IDs and COUNT's all the USERID.. I would like a total of both columns. I've tried warpping the query in a
SELECT COUNT(*) FROM (
but this only counts the ID's which is great, but how do I count the USERID column as well
You seem to want this:
SELECT COUNT(DISTINCT a.ID), COUNT(b.UserID),
COUNT(b.UserID) * 1.0 / COUNT(DISTINCT a.ID)
FROM a INNER JOIN
b
ON someID = someID
WHERE a.ID IN ( SELECT ID FROM c WHERE GROUPID = 9999);
Note: DISTINCT is not a function. It applies to the whole row, so it is misleading to put an expression in parentheses after it.
Also, the GROUP BY is unnecessary.
The 1.0 is because SQL Server does integer arithmetic and this is a simple way to convert a number to a decimal form.
You can use
SELECT COUNT(DISTINCT a.ID) ...
to count all distinct values
Read details here
I believe you want this:
select TotalID,
Total_UserID,
sum(Total_UserID+TotalID) as Total,
Total_UserID/TotalID as Average
from (
SELECT (DISTINCT a.ID) as TotalID
,COUNT(b.UserID) as Total_UserID
FROM a
INNER JOIN b ON someID = someID
WHERE a.ID IN ( SELECT ID FROM c WHERE GROUPID = 9999)
) x
STEP 1
Select data1,name,phone,address from dummyTable limit 4;
From above query, I will get the following result for example:
data1 | name | phone | address
fgh | hjk | 567...| CA
ghjkk | jkjii| 555...| NY
Now, after having the above result I am suppose to match data1 records that I got from above query to existing another table in a database called existingTable which has a same column called data1 in it. If the result above gives data1 value as 'fgh' so I take that 'fgh' and compare with that existingtable column called data1.
STEP 2
Next, after I am finished comparing, I need to apply some condition as follows:
if((results.data1.value).equals(existingTable.data1.value))
then count --
else
count++
So by above condition I am trying to explain, that if the value I got from the result is matched then I do count decrement by 1 and if not then count is incremented by 1.
Summary
I basically wanted to achieve this in one single query, is it possible using PostgreSQL?
I think you can translate that to a simple query:
SELECT d.data1, d.name, d.phone, d.address
, count(*) - 2 * count(e.data1)
FROM (
SELECT data1, name, phone, address
FROM dummytable
-- ORDER BY ???
LIMIT 4
) d
LEFT JOIN existingtable e USING (data1)
GROUP BY d.data1, d.name, d.phone, d.address;
The major ingredient is the LEFT [OUTER] JOIN. Follow the link to the manual.
count(*) counts all rows from dummytable.
count(e.data1) only counts rows from existingtable where a matching data1 exists (count() does not count NULL values). I subtract that twice to match your formula.
About ORDER BY: There is no natural order in a database table. You need to order by something to get predictable results.
If there can be duplicates in existingtable but you want to count every distinct data1 only once, eliminate dupes before you join or use an EXISTS semi-join:
SELECT data1, name, phone, address
, count(*) - 2 * count(EXISTS (
SELECT 1 FROM existingtable e
WHERE e.data1 = d.data1) OR NULL)
FROM (
SELECT data1, name, phone, address
FROM dummytable
-- ORDER BY ???
LIMIT 4
) d
GROUP BY data1, name, phone, address;
The last count works because (TRUE OR NULL) IS TRUE, but (FALSE OR NULL) IS NULL.
I am looking for the AVERAGE (overall) of the MINIMUM number (grouped by person).
My table looks like this:
Rank Name
1 Amy
2 Amy
3 Amy
2 Bart
1 Charlie
2 David
5 David
1 Ed
2 Frank
4 Frank
5 Frank
I want to know the AVERAGE of the lowest scores. For these people, the lowest scores are:
Rank Name
1 Amy
2 Bart
1 Charlie
2 David
1 Ed
2 Frank
Giving me a final answer of 1.5 - because three people have a MIN(Rank) of 1 and the other three have a MIN(Rank) of 2. That's what I'm looking for - a single number.
My real data has a couple hundred rows, so it's not terribly big. But I can't figure out how to do this in a single, simple statement. Thank you for any help.
Try this:
;WITH MinScores
AS
(
SELECT
"Rank",
Name,
ROW_NUMBER() OVER(PARTITION BY Name ORDER BY "Rank") row_num
FROM Table1
)
SELECT
CAST(SUM("Rank") AS DECIMAL(10, 2)) /
COUNT("Rank")
FROM MinScores
WHERE row_num = 1;
SQL Fiddle Demo
Selecting the set of minimum values is straightforward. The cast() is necessary to avoid integer division later. You could also avoid integer division by casting to float instead of decimal. (But you should be aware that floats are "useful approximations".)
select name, cast(min(rank) as decimal) as min_rank
from Table1
group by name
Now you can use the minimums as a common table expression, and select from it.
with minimums as (
select name, cast(min(rank) as decimal) as min_rank
from Table1
group by name
)
select avg(min_rank) avg_min_rank
from minimums
If you happen to need to do the same thing on a platform that doesn't support common table expressions, you can a) create a view of minimums, and select from that view, or b) use the minimums as a derived table.
You might try using a derived table to get the minimums, then get the average minimum in the outer query, as in:
-- Get the avg min rank as a decimal
select avg(MinRank * 1.0) as AvgRank
from (
-- Get everyone's min rank
select min([Rank]) as MinRank
from MyTable
group by Name
) as a
I think the easiest one will be
for max
select name , max_rank = max(rank)
from table
group by name;
for average
select name , avg_rank = avg(rank)
from table
cgroup by name;
I have a table in my database:
Name | Element
1 2
1 3
4 2
4 3
4 5
I need to make a query that for a number of arguments will select the value of Name that has on the right side these and only these values.
E.g.:
arguments are 2 and 3, the query should return only 1 and not 4 (because 4 also has 5). For arguments 2,3,5 it should return 4.
My query looks like this:
SELECT name FROM aggregations WHERE (element=2 and name in (select name from aggregations where element=3))
What do i have to add to this query to make it not return 4?
A simple way to do it:
SELECT name
FROM aggregations
WHERE element IN (2,3)
GROUP BY name
HAVING COUNT(element) = 2
If you want to add more, you'll need to change both the IN (2,3) part and the HAVING part:
SELECT name
FROM aggregations
WHERE element IN (2,3,5)
GROUP BY name
HAVING COUNT(element) = 3
A more robust way would be to check for everything that isn't not in your set:
SELECT name
FROM aggregations
WHERE NOT EXISTS (
SELECT DISTINCT a.element
FROM aggregations a
WHERE a.element NOT IN (2,3,5)
AND a.name = aggregations.name
)
GROUP BY name
HAVING COUNT(element) = 3
It's not very efficient, though.
Create a temporary table, fill it with your values and query like this:
SELECT name
FROM (
SELECT DISTINCT name
FROM aggregations
) n
WHERE NOT EXISTS
(
SELECT 1
FROM (
SELECT element
FROM aggregations aii
WHERE aii.name = n.name
) ai
FULL OUTER JOIN
temptable tt
ON tt.element = ai.element
WHERE ai.element IS NULL OR tt.element IS NULL
)
This is more efficient than using COUNT(*), since it will stop checking a name as soon as it finds the first row that doesn't have a match (either in aggregations or in temptable)
This isn't tested, but usually I would do this with a query in my where clause for a small amount of data. Note that this is not efficient for large record counts.
SELECT ag1.Name FROM aggregations ag1
WHERE ag1.Element IN (2,3)
AND 0 = (select COUNT(ag2.Name)
FROM aggregatsions ag2
WHERE ag1.Name = ag2.Name
AND ag2.Element NOT IN (2,3)
)
GROUP BY ag1.name;
This says "Give me all of the names that have the elements I want, but have no records with elements I don't want"