Foreign key in the first table

Question

I have a question about foreign keys.

How does it work when I want to add a foreign key to the first table that I make that references to the primary key of the second t

Answer 1

here's the syntax of creating a table with Foreign key:

CREATE TABLE table11
(   
    name_id INT NOT NULL,
    team INT,
    PRIMARY KEY(name_id),
    foreign key(team) references table22(team_id)
);



CREATE TABLE table22
(
    team_id INT NOT NULL,
    teamname TEXT,
    PRIMARY KEY(team_id)
);

but there was another problem. a foreign key from a child table cannot reference to a primary key from a parent folder if they do not contain the same type. in your code team was of TEXT and team_id was of INT which cannot be.

Answer 2

Either create the second table first. Or use alter table. That is, create the first table without the reference and then do:

alter table table1 add constraint fk_table1_team
    foreign key (team_id) REFERENCES table2(team_id);

The declaration for table1 would be:

CREATE TABLE table1 (   
    name_id INT NOT NULL,
    team_id INT, 
    PRIMARY KEY(name_id)
);

The reference between the tables should be on the primary key and certainly not on a character column, if an integer is available.