I have a table which has many rows which are same, except for the id column. How can I show only one row for other duplicate row?
id name roll_number
1 a 1
2 b 2
3 a 1
4 b 2
5 c 3
6 d 4
7 d 4
show output like this
id name roll_number
1 a 1
2 b 2
5 c 3
6 d 4
We can use DISTINCT ON here:
SELECT DISTINCT ON (name) id, name, roll_number
FROM yourTable
ORDER BY name, id;
This query is selecting one record with the lowest id from each group of records having the same name.
Simple aggregation using min
select Min(id), name,roll_number
from t
group by name, roll_number
You could use the numpy.unique(filt, trim='fb') function:
>>> import numpy as np
>>> np.unique(array)
This problem requires to "filter out" tuples during the projection based on groups. The solution is to use distinct on.
SELECT DISTINCT ON (name, roll_number) id, name, roll_number
FROM table
ORDER BY name, id;
it basically creates groups by the attributes within the "DISTINCT_ON" and non-deterministically chooses one tuple, which it outputs.
Related
I work in healthcare. In a Postgres database, we have a table member IDs and dates. I'm trying to pull the latest two dates for each member ID.
Simplified sample data:
A 1
B 1
B 2
C 1
C 5
C 7
D 1
D 2
D 3
D 4
Desired result:
A 1
B 1
B 2
C 1
C 5
D 1
D 2
I get a strong feeling this is for a homework assignment and would recommend that you look into partitioning and specifically rank() function by yourself first before looking at my solution.
Moreover, you have not specified how you received the initial result you provided, so I'll have to assume you just did select letter_column, number_column from my_table; to achieve the result.
So, what you actually want here is partition the initial query result into groups by the letter_column and select the first two rows in each. rank() function lets you assign each row a number, counting within groups:
select letter_column,
number_column,
rank() over (partition by letter_column order by number_column) as rank
from my_table;
Since it's a function, you can't use it in a predicate in the same query, so you'll have to build another query around this one, this time filtering the results where rank is over 2:
with ranked_results as (select letter_column,
number_column,
rank() over (partition by letter_column order by number_column asc) as rank
from my_table mt)
select letter_column,
number_column
from ranked_results
where rank < 3;
Here's an SQLFiddle to play around: http://sqlfiddle.com/#!15/e90744/1/0
Hope this helps!
I have a table with following data:
Name
Score
A
2
B
3
A
1
B
3
I want a query which returns the following output.
Name
Score
A
2
A
1
Subtotal: A
3
B
3
B
3
Subtotal: B
6
I am able to get "Subtotal" with group by rollup query but I want to get subtotal along with group column value.
Please help me with some SQL code
If score has at most one value per name, you can use GROUPING SETS`:
select name, sum(score) as score
from t
group by grouping sets ((name, score), (name));
If name is never null, I would just use:
coalesce(name, 'Grouping ' + name)
Otherwise you need to use grouping().
I want to setup a simple query that will filter out any row that contains "A" in the ItemID, but my issue is I also do NOT want to display any journal ID from a different row since it matched "A". I tried googling the solution, but I am sure I am not using the right keywords to find it. I am using microsoft sql 2008, but I am not a database admin so I am not to familiar. I tried using distinct, and I also tried group by, but in this situation it does not work.
This is a simplified version of the table that I am working with:
JournalID ItemID PrimaryKEY
1 A 1
1 B 2
2 A 3
2 C 4
3 B 5
4 D 6
And here is how I would like to make it look:
JournalID ItemID PrimaryKEY
3 B 5
4 D 6
This will exclude any rows where the ItemID is 'A' and also any rows that have the same JournalID as a row where a ItemID was 'A'.
SELECT JournalID, ItemID, PrimaryKEY
FROM TABLE
WHERE JournalID NOT IN (Select JournalID FROM TABLE WHERE ItemID = 'A')
Try this:
SELECT *
FROM table_name
WHERE JournalID
NOT IN (SELECT JournalID
FROM table_name
WHERE ItemID = 'A')
I have a column name and value and I need to write a select to merge all rows with the same name into one row (something like distinct) except when I use distinct then I can't merge/sum value column.
Example:
name value
A 10
B 5
C 20
A 5
C 1
B 5
And the result would be:
A 15
B 10
C 21
This is my select so far, but it is not "merged", it does exactly what my example shows.
select
projects.name,
sum(current_date - (projects_programmers.joined_at))
from projects, projects_programmers
where projects.id = projects_programmers.project_id
group by projects.name, projects_programmers.joined_at
select name, sum(value) value from yourTableName group by name
select distinct
"name", sum("value") over (partition by "name")
from table_name
you can use window function for this
I am using T-SQL.
Say if I have the following
Value Nbr
----- ---
one 6
one 7
one 8
two 6
two 7
three 5
three 3
three 2
In the above table, I need to find which group does not have 6 in it.
In this case, it is three as it does not have 6 in it.
What would be the best approach to do this?
I tried:
select Value from tbl1
where nbr <> 6
group by Value
but did not get the intended result.
select distinct value
from tbl1
where value not in
(
select distinct value
from tbl1
where nbr = 6
)