Error Code: 1005 — there is a wrong primary key reference in your code Usually it’s due to a referenced foreign key field that does not exist. It might be you have a typo mistake, or check case it should be same, or there’s a field-type mismatch. Foreign key-linked fields must match definitions exactly. Some … Read more
Just throwing this into the mix of possible causes, I ran into this when the referencing table column had the same “type” but did not have the same signing. In my case, the referenced table colum was TINYINT UNSIGNED and my referencing table column was TINYINT SIGNED. Aligning both columns solved the issue.
These conditions must be satisfied to not get error 150 re ALTER TABLE ADD FOREIGN KEY: The Parent table must exist before you define a foreign key to reference it. You must define the tables in the right order: Parent table first, then the Child table. If both tables references each other, you must create … Read more
If the tables are innodb you can create it like this: CREATE TABLE accounts( account_id INT NOT NULL AUTO_INCREMENT, customer_id INT( 4 ) NOT NULL , account_type ENUM( ‘savings’, ‘credit’ ) NOT NULL, balance FLOAT( 9 ) NOT NULL, PRIMARY KEY ( account_id ), FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ) ENGINE=INNODB; You have to specify … Read more
Old question but adding answer so that one can get help Its two step process: Suppose, a table1 has a foreign key with column name fk_table2_id, with constraint name fk_name and table2 is referred table with key t2 (something like below in my diagram). table1 [ fk_table2_id ] –> table2 [t2] First step, DROP old … Read more
You would need to manage the referential constraint across databases using a Trigger. Basically you create an insert, update trigger to verify the existence of the Key in the Primary key table. If the key does not exist then revert the insert or update and then handle the exception. Example: Create Trigger dbo.MyTableTrigger ON dbo.MyTable, … Read more
Yep: employee = Employee(first_name=”Name”, last_name=”Name”) employee.type_id = 4 employee.save() ForeignKey fields store their value in an attribute with _id at the end, which you can access directly to avoid visiting the database. The _id version of a ForeignKey is a particularly useful aspect of Django, one that everyone should know and use from time to … Read more
In MySQL, there is no need to give a symbolic name to foreign key constraints. If a name is not given, InnoDB creates a unique name automatically. In any case, this is the convention that I use: fk_[referencing table name]_[referenced table name]_[referencing field name] Example: CREATE TABLE users( user_id int, name varchar(100) ); CREATE TABLE … Read more
To automate this, you could define the foreign key constraint with ON DELETE CASCADE. I quote the the manual for foreign key constraints: CASCADE specifies that when a referenced row is deleted, row(s) referencing it should be automatically deleted as well. Look up the current FK definition like this: SELECT pg_get_constraintdef(oid) AS constraint_def FROM pg_constraint … Read more
How to design table like this in mongodb? First, to clarify some naming conventions. MongoDB uses collections instead of tables. I think there are no foreign keys! Take the following model: student { _id: ObjectId(…), name: ‘Jane’, courses: [ { course: ‘bio101’, mark: 85 }, { course: ‘chem101’, mark: 89 } ] } course { … Read more