Junção externa esquerda atuando como junção interna
Resumo
Meu objetivo é encontrar todos os usuários que já foram atribuídos a uma tarefa, gerar algumas estatísticas em um determinado período e associá-las ao conjunto original de usuários. Quando não existem estatísticas para um usuário específico, quero uma linha na saída para o usuário, masNULL valores para as estatísticas.
Eu tenho uma consulta SQL complexa que se parece com isso (consulta real na parte inferior):
SELECT
user_name, changeday, project_name
sum(hour_delta) AS hours,
FROM ( … ) tasked_users
LEFT OUTER JOIN ( … ) a
ON tasked_users.id=a.assignee_id
WHERE
(changeday IS NULL) OR (changeday >= … AND changeday <= …)
GROUP BY user_name, changeday, a.project_name
ORDER BY user_name, changeday, a.project_name;
Meu desejo é encontrar um grande conjunto de usuários e combiná-los com dados doa mesa; quando existem usuários que não têm entradas correspondentes ema Quero nulos ou0 horas.
Infelizmente, essa consulta retorna apenas linhas para usuários presentes em 'a'. Por exemplo, um determinado conjunto de datas retorna:
{:user_name=>"Gavin", :hours=>0.0, :changeday=>2013-09-08, :project_name=>"Foo"}
{:user_name=>"Steve", :hours=>1.0, :changeday=>2013-09-08, :project_name=>"Bar"}
Diferentes intervalos de datas resultam na descoberta de diferentes usuários. O conteúdo dotasked_users A subconsulta possui 14 pares de ID / nome de usuário distintos. eu precisotodos deles para ser representado no resultado.
Caso isso faça alguma diferença, ou caso você tenha dicas úteis adicionais sobre como melhorar a consulta, veja a consulta completa.
SELECT
user_name,
sum(hour_delta) AS hours,
changeday,
project_name
FROM (
SELECT DISTINCT
users.id,
users.name AS user_name
FROM users
INNER JOIN tasks AS tasks1
ON users.id=tasks1.assignee_id
) tasked_users
LEFT OUTER JOIN
(
SELECT
(
coalesce(cast(nullif(new_value,'') AS float),0) -
coalesce(cast(nullif(old_value,'') AS float),0)
) AS hour_delta,
task_id,
tasks2.assignee_id AS assigned_log,
fixin_id,
projects.name AS project_name,
date_trunc('day',task_log_entries.created_on) AS changeday
FROM task_log_entries
INNER JOIN tasks AS tasks2
ON task_id=tasks2.id
INNER JOIN fixins
ON fixins.id=tasks2.fixin_id
INNER JOIN projects
ON projects.id=fixins.project_id
WHERE field_id=18
) a
ON tasked_users.id=a.assigned_log
WHERE
(changeday IS NULL)
OR
(changeday >= '2013-09-08' AND changeday <= '2013-09-08')
GROUP BY user_name, changeday, a.project_name
ORDER BY user_name, changeday, a.project_name;
Aqui está o resultado deEXPLAIN para a consulta, caso isso ajude (eu não sei como ler isto e derivar o que eu preciso):
GroupAggregate (cost=1116.40..1116.99 rows=13 width=144)"}
-> Sort (cost=1116.40..1116.43 rows=13 width=144)"}
Sort Key: users.name, (date_trunc('day'::text, task_log_entries.created_on)), projects.name"}
-> Hash Left Join (cost=1024.32..1116.16 rows=13 width=144)"}
Hash Cond: (users.id = tasks2.assignee_id)"}
Filter: ((date_trunc('day'::text, task_log_entries.created_on) IS NULL) OR ((date_trunc('day'::text, task_log_entries.created_on) >= '2013-09-08 00:00:00'::timestamp without time zone) AND (date_trunc('day'::text, task_log_entries.created_on) <= '2013-09-08 00:00:00'::timestamp without time zone)))"}
-> HashAggregate (cost=44.07..45.46 rows=139 width=12)"}
-> Hash Join (cost=5.13..40.09 rows=795 width=12)"}
Hash Cond: (tasks1.assignee_id = users.id)"}
-> Seq Scan on tasks tasks1 (cost=0.00..24.01 rows=801 width=4)"}
-> Hash (cost=3.39..3.39 rows=139 width=12)"}
-> Seq Scan on users (cost=0.00..3.39 rows=139 width=12)"}
-> Hash (cost=963.51..963.51 rows=1339 width=30)"}
-> Hash Join (cost=729.23..963.51 rows=1339 width=30)"}
Hash Cond: (fixins.project_id = projects.id)"}
-> Hash Join (cost=727.91..943.79 rows=1339 width=24)"}
Hash Cond: (task_log_entries.task_id = tasks2.id)"}
-> Seq Scan on task_log_entries (cost=0.00..197.46 rows=1339 width=20)"}
Filter: (field_id = 18)"}
-> Hash (cost=717.90..717.90 rows=801 width=12)"}
-> Hash Join (cost=676.87..717.90 rows=801 width=12)"}
Hash Cond: (tasks2.fixin_id = fixins.id)"}
-> Seq Scan on tasks tasks2 (cost=0.00..24.01 rows=801 width=12)"}
-> Hash (cost=589.72..589.72 rows=6972 width=8)"}
-> Seq Scan on fixins (cost=0.00..589.72 rows=6972 width=8)"}
-> Hash (cost=1.14..1.14 rows=14 width=14)"}
-> Seq Scan on projects (cost=0.00..1.14 rows=14 width=14)"}
Aqui está a descrição de todas as tabelas envolvidas. Eu não os recortei para remover qualquer coluna "irrelevante" para que você possa ter certeza de que há conflitos de nome de coluna ambíguos.
app=> \d task_log_entries
Table "public.task_log_entries"
Column | Type | Modifiers
------------+-----------------------------+---------------------------------------------------------------
id | integer | not null default nextval('task_log_entries_id_seq'::regclass)
task_id | integer | not null
user_id | integer |
field_id | integer | not null
created_on | timestamp without time zone | not null default now()
new_value | text |
old_value | text |
Indexes:
"task_log_entries_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"task_log_entries_field_id_fkey" FOREIGN KEY (field_id) REFERENCES log_fields(id)
"task_log_entries_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
"task_log_entries_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL
app=> \d tasks
Table "public.tasks"
Column | Type | Modifiers
----------------+-----------------------------+-----------------------------------------------------
id | integer | not null default nextval('fixins_id_seq'::regclass)
fixin_id | integer | not null
created_on | timestamp without time zone | not null default now()
updated_on | timestamp without time zone | not null default now()
name | character varying(200) | not null
description | text |
blocked_by | character varying(200) |
estimate | double precision |
actual | double precision |
remaining | double precision |
relative_order | integer |
status_id | integer | not null
assignee_id | integer |
Indexes:
"tasks_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"tasks_assignee_id_fkey" FOREIGN KEY (assignee_id) REFERENCES users(id) ON DELETE SET NULL
"tasks_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
"tasks_status_id_fkey" FOREIGN KEY (status_id) REFERENCES task_statuses(id)
Referenced by:
TABLE "task_comments" CONSTRAINT "task_comments_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
TABLE "task_log_entries" CONSTRAINT "task_log_entries_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
TABLE "users_tasks_notifications" CONSTRAINT "users_tasks_notifications_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
app=> \d fixins
Table "public.fixins"
Column | Type | Modifiers
----------------+-----------------------------+-----------------------------------------------------
id | integer | not null default nextval('fixins_id_seq'::regclass)
project_id | integer | not null
created_on | timestamp without time zone | not null default now()
updated_on | timestamp without time zone | not null default now()
name | character varying(200) | not null
description | text | not null
status_id | integer | not null
reporter_id | integer |
assignee_id | integer |
priority_id | integer | not null
severity_id | integer | not null
likelihood_id | integer | not null
maturity | integer | not null default 0
version | character varying(100) |
iteration_id | integer |
relative_order | integer |
kind | character varying(16) | not null default 'Bug'::character varying
specs | character varying(50) |
estimate | double precision |
blocked_by | character varying(200) |
plan_estimate | double precision |
actual | double precision |
remaining | double precision |
promise_date | date |
Indexes:
"fixins_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"fixins_assignee_id_fkey" FOREIGN KEY (assignee_id) REFERENCES users(id) ON DELETE SET NULL
"fixins_iteration_id_fkey" FOREIGN KEY (iteration_id) REFERENCES iterations(id) ON DELETE SET NULL
"fixins_likelihood_id_fkey" FOREIGN KEY (likelihood_id) REFERENCES likelihoods(id)
"fixins_priority_id_fkey" FOREIGN KEY (priority_id) REFERENCES priorities(id)
"fixins_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id)
"fixins_reporter_id_fkey" FOREIGN KEY (reporter_id) REFERENCES users(id) ON DELETE SET NULL
"fixins_severity_id_fkey" FOREIGN KEY (severity_id) REFERENCES severities(id)
"fixins_status_id_fkey" FOREIGN KEY (status_id) REFERENCES statuses(id)
Referenced by:
TABLE "bug_snapshots" CONSTRAINT "bug_snapshots_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE SET NULL
TABLE "comments" CONSTRAINT "comments_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "customers_fixins" CONSTRAINT "customers_fixins_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id)
TABLE "fixins_tags" CONSTRAINT "fixins_tags_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "log_entries" CONSTRAINT "log_entries_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "relationships" CONSTRAINT "relationships_fixin1_id_fkey" FOREIGN KEY (fixin1_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "relationships" CONSTRAINT "relationships_fixin2_id_fkey" FOREIGN KEY (fixin2_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "tasks" CONSTRAINT "tasks_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "users_notifications" CONSTRAINT "users_notifications_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id) ON DELETE CASCADE
TABLE "votes" CONSTRAINT "votes_fixin_id_fkey" FOREIGN KEY (fixin_id) REFERENCES fixins(id)
app=> \d projects
Table "public.projects"
Column | Type | Modifiers
----------------+-------------------------+-------------------------------------------------------
id | integer | not null default nextval('projects_id_seq'::regclass)
name | character varying(50) | not null
link_name | character varying(50) | not null
pain_threshold | integer | not null
wiki_server | character varying(100) |
wiki_wiki | character varying(100) |
wiki_pattern | character varying(1000) |
active | boolean | not null default true
Indexes:
"projects_pkey" PRIMARY KEY, btree (id)
"projects_link_name_key" UNIQUE, btree (link_name)
Referenced by:
TABLE "fixins" CONSTRAINT "fixins_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id)
TABLE "iterations" CONSTRAINT "iterations_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE
TABLE "project_preferences" CONSTRAINT "project_preferences_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id)
TABLE "projects_users_notifications" CONSTRAINT "projects_users_notifications_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id)
TABLE "releases" CONSTRAINT "releases_project_id_fkey" FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE
app=> \d users
Table "public.users"
Column | Type | Modifiers
----------+-----------------------+----------------------------------------------------
id | integer | not null default nextval('users_id_seq'::regclass)
name | character varying(50) | not null
email | character varying(50) |
active | boolean | not null default true
passhash | character varying(40) |
salt | character varying(4) |
Indexes:
"users_pkey" PRIMARY KEY, btree (id)
Referenced by:
TABLE "comments" CONSTRAINT "comments_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "fixins" CONSTRAINT "fixins_assignee_id_fkey" FOREIGN KEY (assignee_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "fixins" CONSTRAINT "fixins_reporter_id_fkey" FOREIGN KEY (reporter_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "log_entries" CONSTRAINT "log_entries_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "project_preferences" CONSTRAINT "project_preferences_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
TABLE "projects_users_notifications" CONSTRAINT "projects_users_notifications_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
TABLE "task_comments" CONSTRAINT "task_comments_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "task_log_entries" CONSTRAINT "task_log_entries_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "tasks" CONSTRAINT "tasks_assignee_id_fkey" FOREIGN KEY (assignee_id) REFERENCES users(id) ON DELETE SET NULL
TABLE "users_notifications" CONSTRAINT "users_notifications_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
TABLE "users_tasks_notifications" CONSTRAINT "users_tasks_notifications_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
app=> \d log_fields
Table "public.log_fields"
Column | Type | Modifiers
--------+------------------------+-----------
id | integer | not null
name | character varying(200) | not null
Indexes:
"log_fields_pkey" PRIMARY KEY, btree (id)
Referenced by:
TABLE "log_entries" CONSTRAINT "log_entries_field_id_fkey" FOREIGN KEY (field_id) REFERENCES log_fields(id)
TABLE "task_log_entries" CONSTRAINT "task_log_entries_field_id_fkey" FOREIGN KEY (field_id) REFERENCES log_fields(id)