I created a table schema but I don't know how I should run the script in this case, because I have constraints on each table that need the creation of the others, is there any method to add the constraint after creation or some other method to leave the correct table schema equal in the script?
I'm using PostgreSQL as a database.
CREATE TABLE IF NOT EXISTS store (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
document VARCHAR(80) NOT NULL,
store_product INTEGER NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (store_product) REFERENCES product (id)
);
CREATE TABLE IF NOT EXISTS product (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
price NUMERIC(15,2) NOT NULL,
store_id INTEGER NOT NULL,
inventory_id INTEGER NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (store_id) REFERENCES store (id),
FOREIGN KEY (inventory_id) REFERENCES inventory (id)
);
CREATE TABLE IF NOT EXISTS inventory (
id INTEGER NOT NULL PRIMARY KEY,
amount INTEGER NOT NULL,
product_id INTEGER NOT NULL,
FOREIGN KEY (product_id) REFERENCES product (id)
);
CodePudding user response:
There are two issues with the foreign key constraints:
1. Adding the Constraints
When there are FKs that link subsets of tables in cycles you can create the tables first, and then add the constraints later.
For example:
CREATE TABLE store (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
document VARCHAR(80) NOT NULL,
store_product INTEGER NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE product (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
price NUMERIC(15,2) NOT NULL,
store_id INTEGER NOT NULL,
inventory_id INTEGER NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE inventory (
id INTEGER NOT NULL PRIMARY KEY,
amount INTEGER NOT NULL,
product_id INTEGER NOT NULL
);
And then:
alter table store add constraint fk1
FOREIGN KEY (store_product) REFERENCES product (id)
deferrable initially deferred;
alter table product add constraint fk2
FOREIGN KEY (store_id) REFERENCES store (id);
alter table product add constraint fk3
FOREIGN KEY (inventory_id) REFERENCES inventory (id);
alter table inventory add constraint fk4
FOREIGN KEY (product_id) REFERENCES product (id);
2. Inserting Data
When inserting data that depends on each other you'll need to decide which row in which table you want to insert first. That's why the example above includes DEFERRABLE INITIALLY DEFERRED
in the first constraint.
This way you can insert in sequence:
- Begin the transaction.
- Insert into
store
--fk1
is not validated yet. - Insert into
inventory
. Validatesfk4
. - Insert into
product
. Validatesfk2
andfk3
. - Commit the transaction. At this point
fk1
will be finally validated.
CodePudding user response:
First create the tables without foreign key constraints and then use ALTER
to alter it for foreign keys that would be a workaround
CREATE TABLE IF NOT EXISTS store (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
document VARCHAR(80) NOT NULL,
store_product INTEGER NOT NULL,
PRIMARY KEY (id),
);
CREATE TABLE IF NOT EXISTS product (
id INTEGER NOT NULL,
nome VARCHAR(255) NOT NULL,
price NUMERIC(15,2) NOT NULL,
store_id INTEGER NOT NULL,
inventory_id INTEGER NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE IF NOT EXISTS inventory (
id INTEGER NOT NULL PRIMARY KEY,
amount INTEGER NOT NULL,
product_id INTEGER NOT NULL,
);
Alter table store
ADD Constraint fk
FOREIGN KEY (store_product) REFERENCES
product (id);
Alter table inventory
ADD Constraint fk1
FOREIGN KEY (product_id) REFERENCES
product (id);
Alter table product
ADD Constraint fk2
FOREIGN KEY (store_id) REFERENCES store (id),
FOREIGN KEY (inventory_id) REFERENCES
inventory (id);