I have two table: User and Team.
They are in a many-to-many relation.
I would like to get all teams of a specific user.
Seams really simple but I can't find the answer anywhere..
Do you know how can I do ?
On the many-to-many relation must be 3rd table. This table contained user_id and team_id connections.
For example:
CREATE TABLE user (
id serial4 NOT NULL,
first_name varchar(200) NOT NULL,
last_name varchar(200) NULL,
CONSTRAINT user_pk PRIMARY KEY (id)
);
CREATE TABLE team (
id serial4 NOT NULL,
team_name varchar NOT NULL,
team_about text NULL,
CONSTRAINT team_pk PRIMARY KEY (id)
);
CREATE TABLE user_team (
id serial4 NOT NULL,
user_id int4 NOT NULL,
team_id int4 NOT NULL,
CONSTRAINT user_team_pk PRIMARY KEY (id)
);
-- filter and select team by user_id
select t.* from examples.team t
inner join examples.user_team usrt on usrt.team_id = t.id
where usrt.user_id = 2;
Related
I need to order my query in a different way i need to group my tables. I need to count how many men are in every department, but organize the query by quantity of people (Not only men, but also women) in every department, in descending way.
This is the diagram and the code of the tables:
Relational model of the tables
CREATE SCHEMA Academico;
CREATE TABLE Academico.PAIS(
ID int NOT NULL,
NOMBRE varchar(30) NOT NULL,
DESCRIPCION varchar(120) NULL,
CONSTRAINT PK_PAIS PRIMARY KEY (ID));
CREATE TABLE Academico.DEPARTAMENTO(
ID int NOT NULL,
NOMBRE varchar(30) NOT NULL,
CODIGO int NOT NULL,
DESCRIPCION varchar(120) NULL,
IDPAIS int NOT NULL,
CONSTRAINT PK_DEPARTAMENTO PRIMARY KEY (ID));
CREATE TABLE Academico.CIUDAD(
ID int NOT NULL,
NOMBRE varchar(255) NOT NULL,
CODIGO int NOT NULL,
DESCRIPCION varchar(120) NULL,
IDDEPARTAMENTO int NOT NULL,
CONSTRAINT PK_CIUDAD PRIMARY KEY (ID));
ALTER TABLE Academico.DEPARTAMENTO
ADD CONSTRAINT FK_DEPARTAMENTO_PAIS FOREIGN KEY(IDPAIS)
REFERENCES Academico.PAIS (ID)
on delete restrict on update restrict;
ALTER TABLE Academico.CIUDAD
ADD CONSTRAINT FK_CIUDAD_DEPARTAMENTO FOREIGN KEY(IDDEPARTAMENTO)
REFERENCES Academico.DEPARTAMENTO (ID)
on delete restrict on update restrict;
CREATE TABLE Academico.SEXO(
ID int NOT NULL,
NOMBRE varchar(30) NOT NULL,
DESCRIPCION varchar(120) NULL,
CONSTRAINT PK_SEXO PRIMARY KEY (ID));
CREATE TABLE Academico.TIPODOCUMENTO(
ID int NOT NULL,
NOMBRE varchar(30) NOT NULL,
DESCRIPCION varchar(120) NULL,
CONSTRAINT PK_TIPODOCUMENTO PRIMARY KEY (ID));
CREATE TABLE Academico.PERSONA(
ID int NOT NULL,
NOMBRE varchar(10) NOT NULL,
APELLIDO varchar(30) NOT NULL,
IDSEXO int NOT NULL REFERENCES Academico.SEXO(id),
IDCIUDAD int NOT NULL REFERENCES Academico.CIUDAD(id),
DOCUMENTO varchar(50) NOT NULL,
IDTIPODOCUMENTO int NOT NULL REFERENCES Academico.TIPODOCUMENTO(id),
FECHANACIMIENTO date NULL CHECK (FECHANACIMIENTO > '1900-01-01'),
FEvarcharEGISTRO date NOT NULL DEFAULT Now() ,
email varchar (355) UNIQUE NOT NULL,
PROFESION varchar(12) NULL,
PERFIL varchar(120) NULL,
CONSTRAINT PK_PERSONA PRIMARY KEY
(ID) );
I tried this two querys that give me the expected results but in a separated way:
select
d.nombre as _departamento, s.nombre as sex, count(1) as total_sexo
from
academico.persona p, academico.sexo s,
academico.ciudad c, academico.departamento d
where
p.idsexo = s.id
and p.idciudad = c.id
and c.iddepartamento = d.id
and upper( s.nombre ) = 'MASCULINO'
group by
d.id,
s.id
order by
d.nombre
-- =======================================================
-- I don't know how to "merge" these two into one query
-- =======================================================
select
d.nombre as _departamento, count(1) as total_gente
from
academico.persona p, academico.ciudad c,
academico.departamento d, academico.sexo s
where
p.idciudad = c.id
and c.iddepartamento = d.id
and p.idsexo = s.id
group by
d.id
order by
total_gente desc
;
I need to get those results with only one query
This is the perfect use for the FILTER (WHERE...) construct.
...
count(1) as total_gente,
count(1) filter (where upper( s.nombre ) = 'MASCULINO') as total_masculino
...
And then take the upper( s.nombre ) = 'MASCULINO' out of the main where clause.
I want to create 3 tables and join them with foreign keys. Unfortunately, it doesn't work and I have no idea where is a mistake.
CREATE TABLE Students (
Student_Id SERIAL PRIMARY KEY,
Name VARCHAR (20) NOT NULL,
Surname VARCHAR (30) NOT NULL,
Date_of_Birth DATE NOT NULL,
Phone INT NOT NULL UNIQUE,
Email VARCHAR(225) NOT NULL UNIQUE,
Course_Id INT
FOREIGN KEY (Course_Id) REFERENCES Course (Course_Id)
);
CREATE TABLE Course (
Course_Id SERIAL PRIMARY KEY,
Student_Id INT NOT NULL,
Teacher_Id INT NOT NULL,
Category VARCHAR (30) NOT NULL,
FOREIGN KEY (Student_Id) REFERENCES Students (Student_Id)
);
CREATE TABLE Teachers (
Teacher_Id SERIAL PRIMARY KEY,
Name VARCHAR (20) NOT NULL,
Surname VARCHAR (30) NOT NULL,
Phone INT NOT NULL UNIQUE,
Salary INT NOT NULL,
Course_Id INT NOT NULL,
FOREIGN KEY (Teacher_Id) REFERENCES Course (Teacher_Id)
);
I should create a Foreign Key to join all three tables.
I get this error every time: relation "course" does not exist
I can't find where is the mistake. Please help.
It appears like you are attempting to crate a many-to-many (M:M) between Students and Teachers with Course as the resolution table. You are close, however, your definition sets up bi-directional relationships. This is normally not necessary. Define Students and Teachers without the FK to Course. Then define Course with a FK to each.
create table students (
student_id serial primary key
, name varchar (20) not null
, surname varchar (30) not null
, date_of_birth date not null
, phone int not null unique
, email varchar(225) not null unique
);
create table teachers (
teacher_id serial primary key
, name varchar (20) not null
, surname varchar (30) not null
, phone int not null unique
, salary int not null
);
create table course (
course_id serial primary key
, student_id int not null
, teacher_id int not null
, category varchar (30) not null
, foreign key (student_id) references students (student_id)
, foreign key (teacher_id) references teachers (teacher_id)
, unique (student_id, teacher_id)
);
If you must define bi-directional FK in Students and Teachers then create the tables without the FK then use alter table after Course is defined to add the FK and make them DEFERRABLE INITIALLY DEFERRED. Necessary for eventual Inserts.
alter table teachers add column course_id int references course(course_id) deferrable initially deferred;
alter table students add column course_id int references course(course_id) deferrable initially deferred;
I'm trying to make schema for my PostgreSQL database basing on the Homegraph concept, however I'm not really sure about correctness of current schema and whether user should have per-structure access or per-device.
I can't find any real-world example of Homegraph concept implementation, and Google seem to not provide such information.
CREATE EXTENSION hstore;
CREATE TABLE users (
id CHAR(32) NOT NULL,
username TEXT NOT NULL,
email TEXT UNIQUE NOT NULL,
password_hash TEXT NOT NULL,
PRIMARY KEY (
id
)
);
CREATE TABLE user_structures (
structure_id CHAR(32) REFERENCES structures (id) ON DELETE CASCADE,
user_id CHAR(32) REFERENCES users (id) ON DELETE CASCADE,
manager BOOL NOT NULL,
PRIMARY KEY (
structure_id,
user_id,
)
);
CREATE TABLE structures (
id CHAR(32) UNIQUE NOT NULL,
label TEXT NOT NULL,
PRIMARY KEY (
id
)
);
CREATE TABLE rooms (
id CHAR(32) UNIQUE NOT NULL,
structure_id CHAR(32) REFERENCES structures (id) ON DELETE CASCADE,
label TEXT NOT NULL,
PRIMARY KEY (
room_id
)
);
CREATE TABLE devices (
id CHAR(32) UNIQUE NOT NULL,
room_id CHAR(32) REFERENCES room (id) ON DELETE CASCADE,
password_hash TEXT NOT NULL,
type TEXT NOT NULL,
traits TEXT[] NOT NULL,
name TEXT NOT NULL,
will_push_state BOOL NOT NULL,
model TEXT NOT NULL,
hw_version TEXT NOT NULL,
sw_version TEXT NOT NULL,
attributes hstore NOT NULL,
PRIMARY KEY (
id,
structure_id
)
);
With regard to the devices table, there is a canonical protobuf that defines each of the fields and their types.
Beyond that, the implementation of the HomeGraph schema is an internal definition within Google's smart home platform and its structure shouldn't matter from a developer perspective.
I have 2 tables:
CREATE TABLE public."user"
(
id integer NOT NULL DEFAULT nextval('user_id_seq'::regclass),
username character varying(256) COLLATE pg_catalog."default",
CONSTRAINT user_pkey PRIMARY KEY (id)
)
CREATE TABLE public.user_tenant
(
user_id integer NOT NULL,
tenant_id integer NOT NULL,
CONSTRAINT user_fk FOREIGN KEY (user_id)
REFERENCES public."user" (id) MATCH SIMPLE
ON UPDATE NO ACTION
ON DELETE CASCADE
)
I need to have unique values (user.username, user_tenant.tenant_id). How can I declare such a constraint?
I would make the username unique, just like the tenant that is in another table. When that is done, you can put a primary key on the user_id and tenant_id:
CREATE TABLE public."user"
(
id integer NOT NULL DEFAULT nextval('user_id_seq'::regclass),
username character varying(256) COLLATE pg_catalog."default" unique,
CONSTRAINT user_pkey PRIMARY KEY (id)
);
CREATE TABLE public.user_tenant
(
user_id integer NOT NULL,
tenant_id integer NOT NULL,
CONSTRAINT user_fk FOREIGN KEY (user_id)
REFERENCES public."user" (id) MATCH SIMPLE
ON UPDATE NO ACTION
ON DELETE CASCADE,
CONSTRAINT user_tenant_pk PRIMARY KEY (user_id, tenant_id)
);
By the way, don't use reserved names like "user" for table names.
You can create a function which can check for uniqueness across multiple tables (example here: Postgres unique combination constraint across tables) but it looks like you may need to the structure of your tables or follow Frank Heikens' answer.
EDIT:
CREATE TABLE public."user"
(
id SERIAL,
username character varying(256) COLLATE pg_catalog."default",
PRIMARY KEY (id)
);
CREATE TABLE public.user_tenant
(
user_id integer NOT NULL,
tenant_id integer NOT NULL,
CONSTRAINT user_fk FOREIGN KEY (user_id)
REFERENCES public."user" (id) MATCH SIMPLE
ON UPDATE NO ACTION
ON DELETE CASCADE
);
CREATE OR REPLACE FUNCTION public.check_user_tenant(user_id integer, tenant_id integer)
RETURNS boolean AS
$$
DECLARE b_result boolean;
BEGIN
SELECT (COUNT(*) = 0) INTO b_result
FROM public.user u
JOIN public.user_tenant ut ON ut.user_id IN (SELECT id
FROM public.user i_u
WHERE i_u.username = u.username)
WHERE u.id = $1 AND ut.tenant_id = $2;
RETURN b_result;
END
$$ LANGUAGE 'plpgsql';
ALTER TABLE public.user_tenant
ADD CONSTRAINT check_filename CHECK
(public.check_user_tenant(user_id, tenant_id));
-- Testing:
insert into public."user" (username) VALUES ('foo');
insert into public.user_tenant (user_id, tenant_id) VALUES (1,3);
insert into public."user" (username) VALUES ('foo');
-- Violates constraint:
insert into public.user_tenant (user_id, tenant_id) VALUES (2,3);
I want to understand inheritance in postgresql, simple whitch columns in whitch tables.
CREATE TABLE users (
id serial PRIMARY KEY,
username VARCHAR UNIQUE NOT NULL,
email VARCHAR NOT NULL,
password_salt VARCHAR,
password_hash VARCHAR,
avatar serial
)
CREATE TABLE groups (
id serial PRIMARY KEY NOT NULL,
name VARCHAR,
email VARCHAR,
avatar serial,
)
CREATE TABLE accounts (
id serial PRIMARY KEY NOT NULL,
name VARCHAR,
avatar serial,
rating json NOT NULL,
);
CREATE TABLE users_to_accounts (
id serial PRIMARY KEY NOT NULL,
start_time DATETIME NOT NULL,
end_time DATETIME,
)
CREATE TABLE account_subscryptions (
user_id serial NOT NULL,
account_id serial NOT NULL,
) INHERITS users_to_accounts
CREATE TABLE account_memberships (
user_id serial NOT NULL,
account_id serial NOT NULL,
) INHERITS users_to_accounts
CREATE TABLE users_to_groups (
id serial PRIMARY KEY NOT NULL,
start_time DATETIME NOT NULL,
end_time DATETIME,
)
CREATE TABLE group_subscryptions (
user_id serial NOT NULL,
group_id serial NOT NULL,
) INHERITS users_to_groups
CREATE TABLE group_memberships (
user_id serial NOT NULL,
group_id serial NOT NULL,
) INHERITS users_to_groups
Now.
1. Is it good design to have foreign keys in child tables an all common data in "abstract" table?
2. Is there any traps in future changes of database with inherited relantion tables?
3. I am all wrong and there is a better way for this schema?
4. I want to create good database schema and generate graphql api in postgraphile, looking in google for half day, did not gave me any one good or best solution, so every link will by great.
It may be usefull for others, I think. Thanks