As the title says, I need to create a query where I SELECT all items from one table and use those items as expressions in another query. Suppose I have the main table that looks like this:
main_table
-------------------------------------
id | name | location | //more columns
---|------|----------|---------------
1 | me | pluto | //
2 | them | mercury | //
3 | we | jupiter | //
And the sub query table looks like this:
some_table
---------------
id | item
---|-----------
1 | sub-col-1
2 | sub-col-2
3 | sub-col-3
where each item in some_table has a price which is in an amount_table like so:
amount_table
--------------
1 | 1000
2 | 2000
3 | 3000
So that the query returns results like this:
name | location | sub-col-1 | sub-col-2 | sub-col-3 |
----------------------------------------------------|
me | pluto | 1000 | | |
them | mercury | | 2000 | |
we | jupiter | | | 3000 |
My query currently looks like this
SELECT name, location, (SELECT item FROM some_table)
FROM main_table
INNER JOIN amount_table WHERE //match the id's
But I'm running into the error more than one row returned by a subquery used as an expression
How can I formulate this query to return the desired results?
you should decide on expected result.
to get one-tp-many relation:
SELECT name, location, some_table.item
FROM main_table
JOIN some_table on true -- or id if they match
INNER JOIN amount_table --WHERE match the id's
to get one-to-one with all rows:
SELECT name, location, (SELECT array_agg(item) FROM some_table)
FROM main_table
INNER JOIN amount_table --WHERE //match the id's
Related
How can I use string_to_array or split_part on another column value.
I want do something like select * from tenants where id IN (select string_to_array(select ancestry from tenants where id = 39,'/'));
-[ RECORD 1 ]-------------+----------------------
id | 1
domain |
subdomain |
name | My Company
login_text |
logo_file_name |
logo_content_type |
logo_file_size |
logo_updated_at |
login_logo_file_name |
login_logo_content_type |
login_logo_file_size |
login_logo_updated_at |
ancestry |
divisible | t
description | Tenant for My Company
use_config_for_attributes | t
default_miq_group_id | 1
source_type |
source_id |
-[ RECORD 3 ]-------------+----------------------
id | 35
domain |
subdomain |
name | Tenant_2
login_text |
logo_file_name |
logo_content_type |
logo_file_size |
logo_updated_at |
login_logo_file_name |
login_logo_content_type |
login_logo_file_size |
login_logo_updated_at |
ancestry | 1
divisible | t
description | Tenant_2
use_config_for_attributes | f
default_miq_group_id | 36
source_type |
source_id |
-[ RECORD 7 ]-------------+----------------------
id | 39
domain |
subdomain |
name | Child_Teanant_202
login_text |
logo_file_name |
logo_content_type |
logo_file_size |
logo_updated_at |
login_logo_file_name |
login_logo_content_type |
login_logo_file_size |
login_logo_updated_at |
ancestry | 1/35
divisible | t
description | Child_Teanant_202
use_config_for_attributes | f
default_miq_group_id | 52
source_type |
source_id |
Use regex to enforce word boundaries:
select *
from tenants
where (select ancestry from tenants where id = 39)
~ ('\y' || id || '\y')
See live demo.
Without the word boundaries an id of 1 would match an ancestry of 123.
Note Postgres's unusual regex for word boundary \y, which elsewhere is \b.
There are two ways to solve this.
One is to simply unnest the elements of ancestry
select *
from tenants
where id in (select a.id::int
from tenants t2
cross join unnest(string_to_array(t2.ancestry, '/')) as a(id)
where t2.id = 39);
Converting the string to an array in order to be able to use the = ANY() operator is a bit tricky, because you need two levels of parentheses plus a type cast to an integer array to make that work:
select *
from tenants
where id = any ((select string_to_array(t2.ancestry, '/')
from tenants t2
where t2.id = 39)::int[]);
Online example
I have a table of users that has a column called order that represents the order in they will be elected.
So, for example, the table might look like:
| id | name | order |
|-----|--------|-------|
| 1 | John | 2 |
| 2 | Mike | 0 |
| 3 | Lisa | 1 |
So, say that now Lisa gets destroyed, I would like that in the same transaction that I destroy Lisa, I am able to update the table so the order is still consistent, so the expected result would be:
| id | name | order |
|-----|--------|-------|
| 1 | John | 1 |
| 2 | Mike | 0 |
Or, if Mike were the one to be deleted, the expected result would be:
| id | name | order |
|-----|--------|-------|
| 1 | John | 1 |
| 3 | Lisa | 0 |
How can I do this in PostgreSQL?
If you are just deleting one row, one option uses a cte and the returning clause to then trigger an update
with del as (
delete from mytable where name = 'Lisa'
returning ord
)
update mytable
set ord = ord - 1
from del d
where mytable.ord > d.ord
As a more general approach, I would really recommend trying to renumber the whole table after every delete. This is inefficient, and can get tedious for multi-rows delete.
Instead, you could build a view on top of the table:
create view myview as
select id, name, row_number() over(order by ord) ord
from mytable
I have a table whose schema along with data (table_name : raw_data) appears to be this :
name | category | clear_date |
A | GOOD | 2020-05-30 |
A | GOOD | 2020-05-30 |
A | GOOD | 2020-05-30 |
A | GOOD | 2020-05-30 |
A | BAD | 2020-05-30 |
A | BAD | 2020-05-30 |
Now if I perform a "groupby" operation using the following statement :
SELECT name, category, date(clear_date), count(clear_date)
FROM raw_data
GROUP BY name, category, date(clear_date)
ORDER BY name
I get the following answer :
name | caetgory | date | count |
A | GOOD |2020-05-30 | 4 |
A | BAD |2020-05-30 | 1 |
A | BAD |2020-05-31 | 1 |
IN order to produce the pivot in following format :
name | category | 2020-05-30 | 2020-05-31 |
A | GOOD | 4 | NULL |
A | BAD | 1 | 1 |
I am using the following query :
select * from crosstab (
'select name, category, date(clear_date), count(clear_date) from raw_data group by name, category, date(clear_date) order by 1,2,3',
'select distinct date(clear_date) from raw_data order by 1'
)
as newtable (
node_name varchar, alarm_name varchar, "2020-05-30" integer, "2020-05-31" integer
)
ORDER BY name
But I am getting results as follows :
name | category | 2020-05-30 | 2020-05-31 |
A | BAD | 4 | 1 |
Can anyone please try to suggest how can i achieve the result mentioned above. It appears crosstab removes the duplicate entry of A automatically.
Not sure if this is possible using crosstab because you have a missing records in some dates. Here is an example how to get expected result but not sure is what you need. Anyway hope this helps.
SELECT r1.*, r2.counter AS "2020-05-30", r3.counter AS "2020-05-31"
FROM (
SELECT DISTINCT name, category
FROM raw_data
) AS r1
LEFT JOIN (
SELECT name, category, count(*) AS counter
FROM raw_data
WHERE clear_date = '2020-05-30'
GROUP BY name, category
) AS r2 ON (r2.category = r1.category AND r2.name = r1.name)
LEFT JOIN (
SELECT name, category, count(*) AS counter
FROM raw_data
WHERE clear_date = '2020-05-31'
GROUP BY name, category
) AS r3 ON (r3.category = r1.category AND r3.name = r1.name)
ORDER BY r1.category DESC;
I need to group fields in a child table in one query in postgres.
I have following data
Stores:
| id | name |
|----|------|
| 1 | abcd |
Features:
| id | store | name | other |
|----|-------|------|-------|
| 1 | 1 | door | metal |
| 2 | 1 | fork | green |
I've got to this query
SELECT
stores.id,
stores.name,
concate_ws(',', features.id, features.name, features.other)
FROM stores
LEFT JOIN features
ON(features.store=stores.id)
WHERE stores.id =1
GROUP BY stores.id, features.id;
This is best I've got so far but yields 2 tuples
1, abcd, (1,door,metal)
1, abcd, (2,fork,green)
I'd like to be able to get one row with the features '|' concatenated like so
1, abcd ,(1,door,metal|2,fork,green)
Use string_agg():
SELECT stores.id,
stores.name,
string_agg(concate_ws(',', features.id, features.name, features.other), '|')
FROM stores
LEFT JOIN features ON features.store=stores.id
WHERE stores.id =1
GROUP BY stores.id, stores.name;
Given this table
| id | name | created_at |
| 1 | test | 2015-02-24 11:13:28.605968 |
| 2 | other | 2015-02-24 13:04:56.968004 |
| 3 | test | 2015-02-24 11:14:24.670765 |
| 4 | test | 2015-02-24 11:15:05.293904 |
And this query which returns only the rows id 2 and id 4.
SELECT DISTINCT ON (documents.name) documents.*
FROM "documents"
ORDER BY documents.name, documents.created_at DESC
How can i return the number of rows affected? Something like
SELECT COUNT(DISTINCT ON (documents.name) documents.*) FROM "documents"
You can use an outer query:
SELECT COUNT(1)
FROM (
SELECT DISTINCT ON (name) *
FROM documents
ORDER BY name, created_at DESC
) alias