Query other fields in tables referenced by FK in junction table

Question

I have a "junction" table ( recipe_ingredients ) that I'm using to handle a many-to-many relationship in my database. Each field in that table is a reference to the PK of another table: recipe_id , ingredient_id , quantity_id , and measure_id . These are the PKs of the metadata , ingredients , quantities , and measurements tables. With the exception of the metadata table, all these tables have only two fields: the PK, and a name or number associated with that PK.

I'm trying to query recipe_ingredients for all rows that have a given recipe_id ... but instead of displaying the PKs in each row with that recipe_id , I want to display the name/number associated with that PK in that table.

So instead of a query that returns this:

recipe_id | ingredient_id | quantity_id | measure_id
----------+---------------+-------------+-----------
1         | 10            | 2           | 3
----------+---------------+-------------+-----------
1         | 12            | 2           | 3
----------+---------------+-------------+-----------
1         | 13            | 5           | 6
----------+---------------+-------------+-----------
...

I'm looking for a query that returns something like this:

recipe_id | ingredient_name | quantity_num | measure_num
----------+-----------------+--------------+------------
1         | Ground cayenne  | 1/2          | tsp
----------+-----------------+--------------+------------
1         | Ground paprika  | 1/2          | tsp
----------+-----------------+--------------+------------
1         | Olive oil       | 1            | tbsp
----------+-----------------+--------------+------------
...

I just started learning SQL, so I only know how to make simple queries to a single table. I don't even know where to begin with this query, except that I may need a kind of join statement. What query could I write to achieve this?

I'm using sqlite3 on Debian.

The recipe_ingredients "junction" table:

CREATE TABLE recipe_ingredients (
    recipe_id               int,
    ingredient_id           int,
    quantity_id             int,
    measure_id              int,
    primary key (recipe_id, ingredient_id),
    foreign key (recipe_id)
            references metadata (recipe_id)
                    on update restrict
                    on delete restrict,
    foreign key (ingredient_id)
            references ingredients (ingredient_id)
                    on update restrict
                    on delete restrict,
    foreign key (quantity_id)
            references quantities (quantity_id)
                    on update restrict
                    on delete restrict,
    foreign key (measure_id)
            references measurements (measure_id)
                    on update restrict
                    on delete restrict
);

These are the foreign tables referenced by the junction table:

create table if not exists ingredients (
    ingredient_id           integer         primary key,
    ingredient_name         text            not null
);

create table if not exists quantities (
    quantity_id             integer         primary key,
    quantity_num            int             not null
);

create table if not exists measurements (
    measure_id              integer         primary key,
    measure_name            text            not null
);

create table if not exists metadata (
    recipe_id               integer         primary key,
    recipe_name             text            not null,
    course_id               int,
    cuisine_id              int,
    servings                int,
    prep_time               int,
    cook_time               int,
    total_time              int,
    foreign key (course_id)
            references courses (course_id)
                    on update restrict
                    on delete restrict,
    foreign key (cuisine_id)
            references cuisine (cuisine_id)
                    on update cascade
                    on delete cascade
);

Answer 1

You can join the junction table with each of the related tables like so:

select
    ri.recipe_id,
    i.ingredient_name,
    q.quantity_num,
    m.measure_num
from recipe_ingredients ri
inner join ingredients i  on i.ingredient_id = ri.ingredient_id
inner join quantities q   on q.quantity_id = ri.quantity_id
inner noin measurements m on m.measure_id = ri.measure_id
where ri.recipe_id = ?

The question mark ( ? ) stands for the recipe_id that you are looking for.