Lets say we have a table 1
1 2 3
a x 10
a y 20
b z 50
As result of the select we want to get the following:
1 2 3
a x 30
a y 30
b z 50
At least the sum of the lines where column 1 is equal. I do the following select and it is working. But the select looks ugly, is there a smarter solution?
SELECT 1, UNNEST(ARRAY_AGG(2)), SUM(3) FROM table1
GROUP BY (1)
You can do a window sum instead:
select col1, col2, sum(col3) over(partition by col1) col3
from mytable
Related
I have the following table with Postgres:
Id Col1 Col2 Col3
1 A 1 x
2 A 0 y
3 A 0 z
4 B 0 x
5 B 1 y
6 C 0 z
As part of a select query, I want to be able to drop duplicates in Col1, based on the highest Col2 values (where will never be multiple highest values per Col1 value), and keep the corresponding Col2, Col3 values.
Desired output:
Id Col1 Col2 Col3
1 A 1 x
5 B 1 y
6 C 0 z
In Postgres, you can use distinct on:
select distinct on (col1) t.*
from t
order by col1, col2 desc;
Let's suppose a have a very simple query in SQL
SELECT Col1,Col2 From Table1
and it gives me result:
Col1 Col2
A 5
A 7
A 2
B 1
B 1
B 4
B 0
C 4
C 1
C 2
I want to count rows in groups made by Col1 and in order made by Col2. If values in Col2 for some rows in group are equal then they should have different numbers, as shown in example
So I want to have
Col1 Col2 Nr
A 5 2
A 7 3
A 2 1
B 0 1
B 1 2
B 1 3
B 4 4
C 4 3
C 1 1
C 2 2
Any ideas how to make it?
If your database supports window functions, use ROW_NUMBER
select col1,col2,row_number() over(partition by col1 order by col2) as nr
from tablename
If your database doesn't support window functions, use
select col1,col2,
(select count(*)+1 from tablename t1 where t1.col1=t.col1 and t1.col2<t.col2) as nr
from tablename t
You can use the row_number window function:
SELECT col1,
col2,
ROW_NUMBER() OVER (PARTITION BY col1 ORDER BY col2 ASC) AS Nr
FROM table1
ORDER BY 1, 2, 3
Let's say I have the dataset that looks like:
col1 col2 col3
a 2 20
a 3 12
a 4 34
b 2 44
c 3 23
c 5 13
....
What I want is a count of col1.
Output:
col1 col2 col3 count
a 2 20 3
a 3 12 3
a 4 34 3
b 2 44 1
c 3 23 2
c 5 13 2
.......
I know I can do by:
with cte as (
select col1, count(*) count
from tab1)
select a.col1,a.col2,a.col3,cte.count
from tab1
join cte on a.col1=cte.col1
But is there any other I can do that without cross apply or cte?
Also, assuming there are more than 3 letters in col1, so I couldn't use sum function either:
SUM(CASE WHEN ItemID = 'a' THEN 1 ELSE 0 END) AS count_a
If you're using SQL Server 2008+, you can use COUNT() OVER():
SELECT *,
COUNT(*) OVER(PARTITION BY col1)
FROM tab1
ONLINE DEMO
TABLE X
col1,col2
1 , 2
1 , 7
1 , 4
1 , 8
2 , 3
2 , 1
2 , 2
3 , 1
3 , 8
3 , 9
3 , 4
4 , 5
4 , 3
4 , 2
4 , 8
4 , 4
I want to retrieve the col1 values that contains in the col2 the values 2 and 4
in this case it will retrieve the values 1 and 4
How can i accomplish this without using the UNION ALL operator ?
The query that i am using is
select distinct col1
from X as A
where col1 = (
select col1 from (
select distinct col1
from X as B
where A.col1 = B.col1 and col2 = 2
union ALL
select distinct col1
from X as C
where A.col1 = C.col1 and col2 = 4
) D
group by col1
having count(col1) > 1
)
It is returning the correct result but i guess is to performance expensive.
Can anyone give me ideas about how to achieve the same result but without unions ?
This problem is called Relational Division, here is one way to do so:
SELECT col1
FROM tablex
WHERE col2 IN (2, 4)
GROUP BY col1
HAVING COUNT(DISTINCT col2) >=2
The HAVING COUNT(col2) >=2 will ensure that the selected col1 must have both the two values 2 and 4 at least.
SQL Fiddle Demo
I think the best performance will come from inner joining the table with itself:
SELECT DISTINCT X1.col1
FROM X X1 INNER JOIN X X2 ON X1.col1=X2.col1
WHERE X1.col2=2 AND X2.col2=4
I have table A with col1 ,col2 with data as
col1 col2
-----------
1 x
2 x
3 x
1 y
2 y
3 y
4 y
1 z
2 z
I want output as:
col1 col2
-----------
1 x
2 x
3 x
4 x
1 y
2 y
3 y
4 y
1 z
2 z
3 z
4 z
Even if values are not there in col2 for max value in col1 i.e '4' query should display up to 4.
SELECT A.col1, B.col2
FROM (SELECT DISTINCT col1 FROM YourTable) A
CROSS JOIN (SELECT DISTINCT col2 FROM YourTable) B
If you want the cartesian product of each possible combination of values in col1 and col2:
Select col1, col2 from
(select distinct col1 from sourcetable) as t1
Cross join
(select distinct col2 from sourcetable) as t2