I have one main table called deliveries and it has one to many relationship with deliveries_languages as dl, deliveries_markets dm and deliveries_tags dt having delivery_id as foreign key. These 3 tables have one to one relation with languages , markets and tags respectively. Additionaly, deliveries, table have one to one relation with companies and have company_is as foreign key. Following is a query that I have written:
SELECT deliveries.*, languages.display_name, markets.default_name, tags.default_name, companies.name
FROM deliveries
JOIN deliveries_languages dl ON dl.delivery_id = deliveries.id
JOIN deliveries_markets dm ON dm.delivery_id = deliveries.id
JOIN deliveries_tags dt ON dt.delivery_id = deliveries.id
JOIN languages ON languages.id = dl.language_id
JOIN markets ON markets.id = dm.market_id
JOIN tags ON tags.id = dt.tag_id
JOIN companies ON companies.id = deliveries.company_id
WHERE
deliveries.name ILIKE '%new%' AND
deliveries.created_by = '5f331347-fb58-4f63-bcf0-702f132f97c5' AND
deliveries.deleted_at IS NULL
LIMIT 10
Here I am getting redundant delivery_ids because for each delivery_id there are multiple languages, markets and tags. I want to use limit on distinct delivery_ids and at the same time, I want those multiple languages, markets and tags to be grouped and populate in single row.
Currently it looks like:
delivery_id | name |languages | markets | tags
------------|------|----------|----------|-----------
1 | d1 |en | au | tag1
1 | d1 |de | sw | tag2
2 | d2 |en | au | tag1
2 | d2 |de | sw | tag2
3 | d3 |en | au | tag1
3 | d3 |de | sw | tag2
Is tere any way that I can have data look like below:
delivery_id | name |languages | markets | tags
------------|------|----------|----------|-----------
1 | d1 |en, de | au,sw | tag1, tag2
2 | d2 |en, de | au,sw | tag1, tag2
3 | d3 |en, de | au,sw | tag2, tag3
P.s. above tables contain only part of data, actual query returns many more columns but above are important one here. Can someone please help me to resolve this issue.
You can use GROUP BY with string_agg like this:
SELECT deliveries.deliver_id, deliver.name,
string_agg(distinct languages.display_name, ',' order by languages.display_name) as langs,
string_agg(distinct markets.default_name, ',' order by markets.default_name) as markets,
string_agg(distinct tags.default_name, ',' order by tags.default_name) as tags,
string_agg(distinct companies.name, ',' order by companies.name) as companies
...
GROUP BY deliveries.deliver_id, deliver.name;
Related
I have a table of users like this:
Table user
id | name | date
1 | alice | 2021-03-28
2 | bob | 2021-03-29
...
And a table with their contacts:
Table contact
id | user_id | contact | has_profile
1 | 1 | facebook | 1
2 | 1 | gmail | 1
3 | 1 | yahoo | 0
4 | 2 | facebook | 0
5 | 2 | gmail | 1
6 | 2 | yahoo | 1
...
I want to write a query that aggregates average rates of the contacts in different dates, so that the result should be:
date | facebook | gmail | yahoo
2021-03-29 | 0.7 | 0.82 | 0.15
2021-03-28 | 0.75 | 0.85 | 0.18
...
I could reach it by the query:
select
u."date",
avg(f.has_profile) as facebook,
avg(g.has_profile) as gmail,
avg(y.has_profile) as yahoo
from user u
join contact f on f.user_id = u.id and f.contact = 'facebook'
join contact g on g.user_id = u.id and g.contact = 'gmail'
join contact y on y.user_id = u.id and y.contact = 'yahoo'
group by u."date"
order by u."date" desc
But the point is that this query depends on the certain contact names in the table contact, so if there are too many ones, the query is too long and complicated to modify. Is there a way to say to Postgresql to extract the names of the contacts automatically and to aggregate over them?
(JSON aggregate as requested in the comments)
demo:db<>fiddle
SELECT
my_date,
jsonb_object_agg(contact, avg) -- 3
FROM (
SELECT
my_date,
contact,
AVG(has_profile) -- 2
FROM
contact c
JOIN users u ON c.user_id = u.id -- 1
GROUP BY my_date, contact
) s
GROUP BY my_date
Join tables
Calculate average values by date and contact
Aggregate these values into a JSON object
Unrelated note: date and user are unrecommended names for database entities because they are reserved keywords. You have to handle them carefully (always use " characters). It's better to rename these properly. Moreover, date is not very descriptive. Maybe login_date or something
Table A contains student names, table B and C contain classes and the presence of students.
I would like to display all students and attend their presence. The problem is that I can not display all students who did not have a checked presence.
Where I checked the presence of students it is ok, but if there is no checked presence in a given class, on a given day and in a given subject- nothing is displayed.
My query:
SELECT student.id_student, CONCAT(student.name,' ' ,student.surname) as 'name_surname',pres_student_present, pres_student_absent, pres_student_justified, pres_student_late, pres_student_rel, pres_student_course, pres_student_delegation, pres_student_note FROM student
LEFT JOIN class ON student.no_classes = class.no_classes
LEFT JOIN pres_student ON student.id_student = pres_student.id_student
WHERE (class.no_classes = '$class' OR NULL AND pres_student_data = '$data' AND pres_student_id_subject = $id_subject OR NULL)
GROUP BY student.surname
ORDER BY student.surname ASC
I want to display name_surname always and any other column should have NULL or 1
like:
Name | present | absent | just | late | rel | delegation | note |
Donald Trump | 1 | | | | | | |
Bush | | | | | | | |
Someone | 1 | | | | | | |
etc...
You should move restrictions on class and pres_studenttables from the WHERE clause to the ON (LEFT join).
In your case when you perform a restriction in the WHERE clause on a table with an outer join, the sql engine consider you are performing an INNER join
SELECT student.id_student
, CONCAT(student.name, ' ', student.surname) AS 'name_surname'
, pres_student_present
, pres_student_absent
, pres_student_justified
, pres_student_late
, pres_student_rel
, pres_student_course
, pres_student_delegation
, pres_student_note
FROM student
LEFT JOIN class
ON student.no_classes = class.no_classes
AND class.no_classes = '$class'
LEFT JOIN pres_student
ON student.id_student = pres_student.id_student
AND pres_student_data = '$data'
AND pres_student_id_subject = $id_subject
GROUP BY student.surname
ORDER BY student.surname ASC
I'm working on a problem, involving these two tables.
books
isbn | title | author
------------+-----------------------------------------+------------------
1840918626 | Hogwarts: A History | Bathilda Bagshot
3458400871 | Fantastic Beasts and Where to Find Them | Newt Scamander
9136884926 | Advanced Potion-Making | Libatius Borage
transactions
id | patron_id | isbn | checked_out_date | checked_in_date
----+-----------+------------+------------------+-----------------
1 | 1 | 1840918626 | 2012-05-05 | 2012-05-06
2 | 4 | 9136884926 | 2012-05-05 | 2012-05-06
3 | 2 | 3458400871 | 2012-05-05 | 2012-05-06
4 | 3 | 3458400871 | 2018-04-29 | 2018-05-02
5 | 2 | 9136884926 | 2018-05-03 | NULL
6 | 1 | 3458400871 | 2018-05-03 | 2018-05-05
7 | 5 | 3458400871 | 2018-05-05 | NULL
the query "Make a list of all book titles and denote whether or not a copy of that book is checked out." so pretty much just the first table with a checked out column.
im trying to SELECT DISTINCT on a sub query with the checkout books first, but that doesn't work. I've researched and others say to accomplish this use a GROUP BY clause instead of DISTINCT but the examples they provide are one column queries and when more columns are added it doesn't work.
this is my closest attempt
SELECT DISTINCT ON (title)
title, checked_out
FROM(
SELECT b.title, t.checked_in_date IS NULL AS checked_out
FROM transactions t
natural join books b
ORDER BY checked_out DESC
) t;
or you can join only transactions where books are not checked in:
SELECT b.title, t.isbn IS NOT NULL AS checked_out
, t.checked_out_date
FROM books b
LEFT JOIN transactions t ON t.isbn = b.isbn AND t.checked_in_date IS NULL
ORDER BY checked_out DESC
I adjusted your attempt a little bit. Basically I changed the way your data is joined
SELECT DISTINCT ON (title)
title, checked_out
FROM(
SELECT b.title, t.checked_in_date IS NULL AS checked_out
FROM books b
LEFT OUTER JOIN transactions t USING (isbn)
ORDER BY checked_out DESC
) t;
I have three tables in Postgres. They are all about a single event (an occurrence, not "sports event"). Each table is about a specific item during the event.
table_header columns
gid, start_timestamp, end_timestamp, location, positions
table_item1 columns
gid, side, visibility, item1_timestamp
table_item2 columns
gid, position_id, name, item2_timestamp
I've tried the following query:
SELECT h.gid, h.location, h.start_timestamp, h.end_timestamp, i1.side,
i1.visibility, i2.position_id, i2.name, i2.item2_timestamp AS timestamp
FROM tablet_header AS h
LEFT OUTER JOIN table_item1 i1 on (i1.gid = h.gid)
LEFT OUTER JOIN table_item2 i2 on (i2.gid = i1.gid AND
i1.item1_timestamp = i2.item2_timestamp)
WHERE h.start_timestamp BETWEEN '2016-03-24 12:00:00'::timestamp AND now()::timestamp
The problem is that I'm losing some data from rows when item1_timestamp and item2_timestamp do not match.
So if I have in table_item1 and table_item2:
gid | item1_timestamp | side gid | item2_timestamp | name
---------------------------- -----------------------------------
1 | 17:00:00 | left 1 | 17:00:00 | charlie
1 | 17:00:05 | right 1 | 17:00:03 | frank
1 | 17:00:10 | left 1 | 17:00:06 | dee
I would want the final output to be:
gid | timestamp | side | name
-----------------------------
1 | 17:00:00 | left | charlie
1 | 17:00:03 | | frank
1 | 17:00:05 | right |
1 | 17:00:06 | | dee
1 | 17:00:10 | left |
based purely on the timestamp (and gid). Naturally I would have the header info in there too, but that's trivial.
I tried playing around with the query I posted used different JOINs and UNIONs, but I cannot seem to get it right. The one I posted gives the best results I could manage, but it's incomplete.
Side note: every minute or so there will be a new "event". So the gid will be unique to each event and the query needs to ensure that each dataset is paired with data from the same gid. Which is the reason for my i1.gid = h.gid lines. Data between different events should not be compared.
select t1.gid, t1.timestamp, t1.side, t2.name
from t1
left join t2 on t2.timestamp=t1.timestamp and t2.gid=t1.gid
union
select t1.gid, t1.timestamp, t1.side, t2.name
from t2
left join t1 on t2.timestamp=t1.timestamp and t2.gid=t1.gid
I have two tables, table A has ID column whose values are comma separated, each of those ID value has a representation in table B.
Table A
+-----------------+
| Name | ID |
+------------------
| A1 | 1,2,3|
| A2 | 2 |
| A3 | 3,2 |
+------------------
Table B
+-------------------+
| ID | Value |
+-------------------+
| 1 | Apple |
| 2 | Orange |
| 3 | Mango |
+-------------------+
I was wondering if there is an efficient way to do a select where the result would as below,
Name, Value
A1 Apple, Orange, Mango
A2 Orange
A3 Mango, Orange
Any suggestions would be welcome. Thanks.
You need to first "normalize" table_a into a new table using the following:
select name, regexp_split_to_table(id, ',') id
from table_a;
The result of this can be joined to table_b and the result of the join then needs to be grouped in order to get the comma separated list of the names:
select a.name, string_agg(b.value, ',')
from (
select name, regexp_split_to_table(id, ',') id
from table_a
) a
JOIN table_b b on b.id = a.id
group by a.name;
SQLFiddle: http://sqlfiddle.com/#!12/77fdf/1
There are two regex related functions that can be useful:
http://www.postgresql.org/docs/current/static/functions-string.html
regexp_split_to_table()
regexp_split_to_array()
Code below is untested, but you'd use something like it to match A and B:
select name, value
from A
join B on B.id = ANY(regexp_split_to_array(A.id, E'\\s*,\\s*', 'g')::int[]))
You can then use array_agg(value), grouping by name, and format using array_to_string().
Two notes, though:
It won't be as efficient as normalizing things.
The formatting itself ought to be done further down, in your views.