I want to get the last comment in a conversation between two people.
My table structure as follows:
Table "public.comments"
Column | Type | Modifiers | Storage | Stats target | Description
-------------+-----------------------------+-------------------------------------------------------+----------+--------------+-------------
id | integer | not null default nextval('comments_id_seq'::regclass) | plain | |
body | text | not null | extended | |
target_id | integer | | plain | |
target_type | character varying(255) | | extended | |
created_at | timestamp without time zone | not null | plain | |
updated_at | timestamp without time zone | not null | plain | |
user_id | integer | | plain | |
My Attempt:
SELECT
comments.id,
max(SELECT id comments.created_at),
CASE
WHEN user_id = 1 THEN CONCAT(user_id,'_',target_id)
WHEN target_id = 1 THEN CONCAT(target_id,'_',user_id)
END
FROM comments
WHERE
comments.user_id = 1
OR
(comments.target_type = 'User'
AND
comments.target_id = 1)
GROUP BY
CASE
WHEN user_id = 1 THEN CONCAT(user_id,'_',target_id)
WHEN target_id = 1 THEN CONCAT(target_id,'_',user_id)
END
So I figured out how to group the comments but how to order by created_at and get the latest id and information is where I'm stuck.
Related
I have a function below (is_organizer) that works, and lets me use this method as a computed field in Hasura. The function below (is_chapter_member) which is almost identical, doesn't work.
WORKS
CREATE OR REPLACE FUNCTION is_organizer(event_row events, hasura_session json)
RETURNS boolean AS $$
SELECT EXISTS (
SELECT 1
FROM event_organizers o
WHERE
o.user_id::text = hasura_session->>'x-hasura-user-id'
AND
(event_row.id = o.event_id OR event_row.event_template_id = o.event_template_id)
);
$$ LANGUAGE SQL STRICT IMMUTABLE;
BROKEN
CREATE OR REPLACE FUNCTION is_chapter_member(c chapters, hasura_session json)
RETURNS boolean AS $$
SELECT EXISTS (
SELECT 1
FROM chapter_members m
WHERE
m.user_id::text = hasura_session->>'x-hasura-user-id'
AND
c.chapter_id = m.chapter_id
);
$$ LANGUAGE SQL STRICT IMMUTABLE;
When attempting to add this function (not call it, just create it) Postgres gives me the following error:
ERROR: missing FROM-clause entry for table "c"
LINE 9: c.chapter_id = m.chapter_id
Why would a function param need a where clause? Table dumps below...
Table "public.chapters"
Column | Type | Collation | Nullable | Default
-----------------+--------------------------+-----------+----------+--------------------------------------
id | integer | | not null | nextval('chapters_id_seq'::regclass)
title | text | | not null |
slug | text | | not null |
description | jsonb | | |
avatar_url | text | | |
photo_url | text | | |
region | text | | |
maps_api_result | jsonb | | |
lat | numeric(11,8) | | |
lng | numeric(11,8) | | |
created_at | timestamp with time zone | | not null | now()
updated_at | timestamp with time zone | | not null | now()
deleted_at | timestamp with time zone | | |
Table "public.chapter_members"
Column | Type | Collation | Nullable | Default
------------+--------------------------+-----------+----------+---------
user_id | integer | | not null |
chapter_id | integer | | not null |
created_at | timestamp with time zone | | not null | now()
updated_at | timestamp with time zone | | not null | now()
Table "public.events"
Column | Type | Collation | Nullable | Default
-------------------+-----------------------------+-----------+----------+---------------------------------------------------
id | integer | | not null | nextval('events_id_seq'::regclass)
event_template_id | integer | | not null |
venue_id | integer | | |
starts_at | timestamp without time zone | | not null |
duration | interval | | not null |
title | text | | |
slug | text | | |
description | text | | |
photo_url | text | | |
created_at | timestamp without time zone | | not null | now()
updated_at | timestamp without time zone | | not null | now()
deleted_at | timestamp without time zone | | |
ends_at | timestamp without time zone | | | generated always as (starts_at + duration) stored
Table "public.event_organizers"
Column | Type | Collation | Nullable | Default
-------------------+---------+-----------+----------+----------------------------------------------
id | integer | | not null | nextval('event_organizers_id_seq'::regclass)
user_id | integer | | not null |
event_id | integer | | |
event_template_id | integer | | |
This turned out to be using an incorrect column name in the broken function. chapter_id should have just been id on the c argument. I took Richard's prompt and tried putting parens around the arg like (c).chapter_id. This then correctly told me that chapter_id doesn't exist, and allowed me to fix the issue.
I have implemented a tagging system in my application, using Postgres 9.6. There are three tables.
Projects
Table "public.project"
Column | Type | Collation | Nullable | Default
-------------+-----------------------------+-----------+----------+---------------------------------
id | integer | | not null | nextval('tag_id_seq'::regclass)
name | character varying(255) | | not null |
user_id | integer | | |
Tags
Table "public.tag"
Column | Type | Collation | Nullable | Default
-------------+-----------------------------+-----------+----------+---------------------------------
id | integer | | not null | nextval('tag_id_seq'::regclass)
tag | character varying(255) | | not null |
user_id | integer | | |
is_internal | boolean | | not null | false
Project tags
Column | Type | Collation | Nullable | Default
------------------+-----------------------------+-----------+----------+-----------------------------------------
id | integer | | not null | nextval('project_tag_id_seq'::regclass)
tag_id | integer | | not null |
project_id | integer | | | |
user_id | integer | | not null |
Now I want to get a list of all the projects, annotated with a column that indicates (for a particular tag) whether it has that tag.
So I'd like the results to look like this:
id name has_favorite_tag
1 foo true
2 bar false
3 baz false
This is my query so far:
select project.*, CASE(XXXX) as has_project_tag
from project p
join (select * from project_tag where tag_id=1) pt on p.id=pt.project_id
I know that I want to use CASE to be true when the length of project_tag matches is greater than 0 - but how do I do this?
(In reality the project table has many more fields, of course.)
Here's a possibility (unfiltered for tag_id; add to inner select if necessary):
select project.*, exists(select * from project_tag where id=project.id) as has_project_tag from project;
psql (9.6.1, server 9.5.5)
employees
Column | Type | Modifiers | Storage | Stats target | Description
----------------+-----------------------------+-----------------------------------------------------------------+----------+--------------+---- ---------
employee_id | integer | not null default nextval('employees_employee_id_seq'::regclass) | plain | |
first_name | character varying(20) | | extended | |
last_name | character varying(25) | not null | extended | |
email | character varying(25) | not null | extended | |
phone_number | character varying(20) | | extended | |
hire_date | timestamp without time zone | not null | plain | |
job_id | character varying(10) | not null | extended | |
salary | numeric(8,2) | | main | |
commission_pct | numeric(2,2) | | main | |
manager_id | integer | | plain | |
department_id | integer
For self education I'd like to use a variable.
The result of this request would suit me:
hr=> select last_name, char_length(last_name) as Length from employees where substring(last_name from 1 for 1) = 'H' order by last_name;
last_name | length
-----------+--------
Hartstein | 9
Higgins | 7
Hunold | 6
(3 rows)
But for self education I'd like to use a variable:
\set chosen_letter 'H'
hr=> select last_name, char_length(last_name) as Length from employees where substring(last_name from 1 for 1) = :chosen_letter order by last_name;
ERROR: column "h" does not exist
LINE 1: ...ployees where substring(last_name from 1 for 1) = H order by...
^
Those apostrophes seems to ruin everything. And I can't cope with the problem.
Could you help me understand how to use variable to acquire the result as above?
Try using:
\set chosen_letter '''H'''
I need help with a bit of a crazy single-query goal please that I'm not sure if GROUP BY or sub-SELECT applies to?
The following query:
SELECT id_finish, description, inside_rate, outside_material, id_part, id_metal
FROM parts_finishing AS pf
LEFT JOIN parts_finishing_descriptions AS fd ON (pf.id_description=fd.id);
Returns the results like the following:
+-------------+-------------+------------------+--------------------------------+
| description | inside_rate | outside_material | id_part - id_finish - id_metal |
+-------------+-------------+------------------+--------------------------------+
| Nickle | 0 | 33.44 | 4444-44-44, 5555-55-55 |
+-------------+-------------+------------------+--------------------------------+
| Bend | 11.22 | 0 | 1111-11-11 |
+-------------+-------------+------------------+--------------------------------+
| Pack | 22.33 | 0 | 2222-22-22, 3333-33-33 |
+-------------+-------------+------------------+--------------------------------+
| Zinc | 0 | 44.55 | 6000-66-66 |
+-------------+-------------+------------------+--------------------------------+
I need the results to return in the fashion below but there are catches:
I need to group by either the inside_rate column or the outside_material column but ORDER BY the description column but not ORDER BY or sort them by price (inside_rate and outside_material are the prices). So we know that they belong to a group if inside_rate is 0 or to the other group if outside_material is 0.
I need to ORDER BY the description column desc secondary after they are returned per group.
I need to return a list of parts (composed of three separate columns) for that inside/outside group / price for that finishing.
Stack format fix.
+-------------+-------------+------------------+--------------------------------+
| description | inside_rate | outside_material | id_part - id_finish - id_metal |
+-------------+-------------+------------------+--------------------------------+
| Bend | 11.22 | 0 | 1111-11-11 |
+-------------+-------------+------------------+--------------------------------+
| Pack | 22.33 | 0 | 2222-22-22, 3333-33-33 |
+-------------+-------------+------------------+--------------------------------+
| Nickle | 0 | 33.44 | 4444-44-44, 5555-55-55 |
+-------------+-------------+------------------+--------------------------------+
| Zinc | 0 | 44.55 | 6000-66-66 |
+-------------+-------------+------------------+--------------------------------+
The tables I'm working with and their data types:
Table "public.parts_finishing"
Column | Type | Modifiers
------------------+---------+-------------------------------------------------------------
id | bigint | not null default nextval('parts_finishing_id_seq'::regclass)
id_part | bigint |
id_finish | bigint |
id_metal | bigint |
id_description | bigint |
date | date |
inside_hours_k | numeric |
inside_rate | numeric |
outside_material | numeric |
sort | integer |
Indexes:
"parts_finishing_pkey" PRIMARY KEY, btree (id)
Table "public.parts_finishing_descriptions"
Column | Type | Modifiers
------------+---------+------------------------------------------------------------------
id not null | bigint | default nextval('parts_finishing_descriptions_id_seq'::regclass)
date | date |
description | text |
rate_hour | numeric |
type | text |
Indexes:
"parts_finishing_descriptions_pkey" PRIMARY KEY, btree (id)
The second table's first column is just id. (Why are we still dealing with a 1024 static width layout in 2015?)
I'd make an SQL fiddle though it refuses to load for me regardless of the browser.
Not entirely sure I understand your question. Might look like this:
SELECT pd.description, pf.inside_rate, pf.outside_material
, concat_ws(' - ', pf.id_part::text
, pf.id_finish::text
, pf.id_metal::text) AS id_part_finish_metal
FROM parts_finishing pf
LEFT JOIN parts_finishing_descriptions fd ON pf.id_description = fd.id
ORDER BY (pf.inside_rate = 0) -- 1. sorts group "inside_rate" first
, pd.description DESC NULLS LAST -- 2. possible NULL values last
;
In PostgreSQL 9 on CentOS 6 there are 60000 records in pref_users table:
# \d pref_users
Table "public.pref_users"
Column | Type | Modifiers
------------+-----------------------------+--------------------
id | character varying(32) | not null
first_name | character varying(64) | not null
last_name | character varying(64) |
login | timestamp without time zone | default now()
last_ip | inet |
(... more columns skipped...)
And another table holds around 500 ids of users which are not allowed to play anymore:
# \d pref_ban2
Table "public.pref_ban2"
Column | Type | Modifiers
------------+-----------------------------+---------------
id | character varying(32) | not null
first_name | character varying(64) |
last_name | character varying(64) |
city | character varying(64) |
last_ip | inet |
reason | character varying(128) |
created | timestamp without time zone | default now()
Indexes:
"pref_ban2_pkey" PRIMARY KEY, btree (id)
In a PHP script I am trying to display all 60000 users from pref_users in a jQuery-dataTable. And I would like to mark the banned users (the users found in pref_ban2).
Which means I need a column named ban for each record in my query holding true or false.
So I am trying a left outer join query:
# select
b.id, -- how to make this column a boolean?
u.id,
u.first_name,
u.last_name,
u.city,
u.last_ip,
to_char(u.login, 'DD.MM.YYYY') as day
from pref_users u left outer join pref_ban2 b on u.id=b.id
limit 10;
id | id | first_name | last_name | city | last_ip | day
----+----------+-------------+-----------+-------------+-----------------+------------
| DE1 | Alex | | Bochum | 2.206.0.224 | 21.11.2014
| DE100032 | Княжна Мэри | | London | 151.50.61.131 | 01.02.2014
| DE10011 | Aлександр Ш | | Симферополь | 37.57.108.13 | 01.01.2014
| DE10016 | Semen10 | | usa | 69.123.171.15 | 25.06.2014
| DE10018 | Горловка | | Горловка | 178.216.97.214 | 25.09.2011
| DE10019 | -Дмитрий- | | пермь | 5.140.81.95 | 21.11.2014
| DE10047 | Василий | | Cумы | 95.132.42.185 | 25.07.2014
| DE10054 | Maedhros | | Чикаго | 207.246.176.110 | 26.06.2014
| DE10062 | ssergw | | москва | 46.188.125.206 | 12.09.2014
| DE10086 | Вадим | | Тула | 109.111.26.176 | 26.02.2012
(10 rows)
As you can see the b.id column above is empty - because these 10 users aren't banned.
How to get a false value in that column instead of a String?
And I am not after some coalesceor case expression, but am looking for "the proper" way to do such a query.
"IS NULL" and "IS NOT NULL" return a boolean, so this should make it easy.
I think this is all you need?
SELECT
b.id IS NOT NULL as is_banned, -- The value of "is_banned" will be a boolean
Not sure if you need the "NOT" or not, but you'll get a bool either way.
A CASE or COALESCE statement with an outer join IS the proper way to do this.
select
CASE
WHEN b.id IS NULL THEN true
ELSE false
END AS banned,
u.id,
u.first_name,
u.last_name,
u.city,
u.last_ip,
to_char(u.login, 'DD.MM.YYYY') as day
from pref_users u
left outer join pref_ban2 b
on u.id=b.id
limit 10;