In my postgres table, I have two columns of interest: id and name - my goal is to only keep records where id has more than one value in name. In other words, would like to keep all records of ids that have multiple values and where at least one of those values is B
UPDATE: I have tried adding WHERE EXISTS to the queries below but this does not work
The sample data would look like this:
> test
id name
1 1 A
2 2 A
3 3 A
4 4 A
5 5 A
6 6 A
7 7 A
8 2 B
9 1 B
10 2 B
and the output would look like this:
> output
id name
1 1 A
2 2 A
8 2 B
9 1 B
10 2 B
How would one write a query to select only these kinds records?
Based on your description you would seem to want:
select id, name
from (select t.*, min(name) over (partition by id) as min_name,
max(name) over (partition by id) as max_name
from t
) t
where min_name < max_name;
This can be done using EXISTS:
select id, name
from test t1
where exists (select *
from test t2
where t1.id = t2.id
and t1.name <> t2.name) -- this will select those with multiple names for the id
and exists (select *
from test t3
where t1.id = t3.id
and t3.name = 'B') -- this will select those with at least one b for that id
Those records where for their id more than one name shines up, right?
This could be formulated in "SQL" as follows:
select * from table t1
where id in (
select id
from table t2
group by id
having count(name) > 1)
Related
I have table with self-related foreign keys and can not get how I can receive firs child or descendant which meet condition. My_table structure is:
id
parent_id
type
1
null
union
2
1
group
3
2
group
4
3
depart
5
1
depart
6
5
unit
7
1
unit
I should for id 1 (union) receive all direct child or first descendant, excluding all groups between first descendant and union. So in this example as result I should receive:
id
type
4
depart
5
depart
7
unit
id 4 because it's connected to union through group with id 3 and group with id 2 and id 5 because it's connected directly to union.
I've tried to write recursive query with condition for recursive part: when parent_id = 1 or parent_type = 'depart' but it doesn't lead to expected result
with recursive cte AS (
select b.id, p.type_id
from my_table b
join my_table p on p.id = b.parent_id
where b.id = 1
union
select c.id, cte.type_id
from my_table c
join cte on cte.id = c.parent_id
where c.parent_id = 1 or cte.type_id = 'group'
)
Here's my interpretation:
if type='group', then id and parent_id are considered in the same group
id#1 and id#2 are in the same group, they're equals
id#2 and id#3 are in the same group, they're equals
id#1, id#2 and id#3 are in the same group
If the above is correct, you want to get all the first descendent of id#1's group. The way to do that:
Get all the ids in the same group with id#1
Get all the first descendants of the above group (type not in ('union', 'group'))
with recursive cte_group as (
select 1 as id
union all
select m.id
from my_table m
join cte_group g
on m.parent_id = g.id
and m.type = 'group')
select mt.id,
mt.type
from my_table mt
join cte_group cg
on mt.parent_id = cg.id
and mt.type not in ('union','group');
Result:
id|type |
--+------+
4|depart|
5|depart|
7|unit |
Sounds like you want to start with the row of id 1, then get its children, and continue recursively on rows of type group. To do that, use
WITH RECURSIVE tree AS (
SELECT b.id, b.type, TRUE AS skip
FROM my_table b
WHERE id = 1
UNION ALL
SELECT c.id, c.type, (c.type = 'group') AS skip
FROM my_table c
JOIN tree p ON c.parent_id = p.id AND p.skip
)
SELECT id, type
FROM tree
WHERE NOT skip
I want to group the records by relation.
products table:
id
price
1
100
2
200
3
300
4
400
product_properties table:
id
productId
propertyId
1
1
2
2
1
3
3
2
2
4
2
3
5
3
4
6
4
4
The query should select lowest price group by product_properties. I mean, If products have same properties in product_properties, query should return product that has lowest price.
So, For these tables query should return products that have ids 1,3.
I use TypeORM, I tried join the relation and distinct on relation alias name but its not worked.
How can I achieve this?
I wrote two variants query for you:
-- variant 1
select distinct t1.product_id from (
select
pr.price, pp.product_id, pp.property_id, min(pr.price) OVER(PARTITION BY pp.property_id) as min_price
from
test.product_properties pp
inner join
test.products pr on pp.product_id = pr.id
) t1
where
t1.price = t1.min_price;
-- variant 2
select distinct t1.product_id from test.product_properties t1
inner join test.products t2 on t1.product_id = t2.id
inner join (
select
pp.property_id, min(pr.price) as min_price
from
test.product_properties pp
inner join
test.products pr on pp.product_id = pr.id
group by pp.property_id
) t3 on t3.property_id = t1.property_id and t3.min_price = t2.price;
I have this datatables:
table1
id category
-------------
1 a
2 b
3 c
table2
id heading category_id
----------------------
1 name 1
2 adddress 2
3 phone 3
4 email 1
I want to group this table and display the latest data for that the following query was I used:
SELECT news.id,news.image,news.heading,news.description,
news.date,news.category_id,categories.category
FROM `news`
INNER JOIN categories On news.category_id=categories.id
group by category_id
But I didnt get the latest data that I entered.
Try the query below:
SELECT *
FROM table2 AS tb2 LEFT JOIN table1 AS tb1 ON tb2.category_id = tb1.id
ORDER BY tb1.id
GROUP BY tb2.category_id
In postgresql i can't execute this code
SELECT name, SUM(sws) as sws, SUM(sws) over (partition by sws) swsrange FROM professoren
JOIN vorlesungen on persnr = gelesenvon
group by name
order by sws desc
The Error code is this:
FEHLER: Spalte »vorlesungen.sws« muss in der GROUP-BY-Klausel erscheinen oder in einer Aggregatfunktion verwendet werden
LINE 1: SELECT name, SUM(sws) as sws, SUM(sws) over (partition by s...
which means he wants "sws" must be in the group by or in a aggregation function (which it actually is).
UPDATE:
i changed it to
SELECT name, SUM(sws) as swscount, SUM(sws) over (partition by name) swsrange FROM professoren
JOIN vorlesungen on persnr = gelesenvon
group by name, sws
the output is:
Augustinus,2,2|Kant,8,4|Popper,2,2|Russel,2,5|Russel,6,5|Sokrates,2,6|Sokrates,8,6
but it should be like the first Column is the name, the second is the sum() of all lessons he gives and the third is like a ranking who has the most lessons:
Sokrates,10,1|Kant,8,2|Russel,8,2|Augustinus,2,3|Popper,2,3
i can't see the issue here.
thanks for your help.
You specified SUM(sws) over (partition by sws) but sws is not specified in GROUP BY.
After your edit of question, could it be what you are looking for?:
DROP TABLE T2;
CREATE TABLE T2 (NAME VARCHAR(20), SWSCOUNT INT)
;
INSERT INTO T2 VALUES ('Augustinus',2), ('Kant',8), ('Popper',2), ('Russel',2), ('Russel',6),('Sokrates',2),('Sokrates',8);
SELECT * FROM T2;
SELECT *, DENSE_RANK() OVER (ORDER BY swscount DESC)
FROM (SELECT NAME, SUM(SWSCOUNT) AS SWSCOUNT
FROM T2
GROUP BY NAME) X
Ouput:
name swscount
1 Augustinus 2
2 Kant 8
3 Popper 2
4 Russel 2
5 Russel 6
6 Sokrates 2
7 Sokrates 8
name swscount dense_rank
1 Sokrates 10 1
2 Kant 8 2
3 Russel 8 2
4 Popper 2 3
5 Augustinus 2 3
I have 2 tables
students:
id | name | age
1 abc 20
2 xyz 21
scores:
id | studentid | marks
1 1 20
2 2 22
3 2 20
4 1 22
5 1 20
where studentid is foreign key to students table
When a do
select studentid
from scores
where marks=20;
I get the following result
1, 2, 1
But if want the name of the student name and when I do a join using
select t1.name
from students t1
inner join scores t2 on t1.id = t2.studentid
where t2.marks=20;
I get xyz,abc,abc Though the ouput is correct is there any way I can maintain the order in which scores are listed in the scores table? I should get abc,xyz,abc as output. I tried using subquery as well
SELECT name
FROM students
WHERE ID IN ( select studentid from scores where marks=20) ;
but that also did not give me correct order. How can this be achieved using CTEs (common table expressions)? I tried the follownig cte but it did not work
with cte as(
select t2.id, t1.name
from students t1
inner join scores t2 on t1.id = t2.studentid
where t2.marks=20)
select name from cte order by id
You can order by a column not present in select list:
select t1.name
from students t1
inner join scores t2 on t1.id = t2.student_id
where t2.marks=20
order by t2.id;
name
------
abc
xyz
abc
(3 rows)