Yes – you can have a foreign key that references a unique index in another table. CREATE UNIQUE INDEX UX01_YourTable ON dbo.YourTable(SomeUniqueColumn) ALTER TABLE dbo.YourChildTable ADD CONSTRAINT FK_ChildTable_Table FOREIGN KEY(YourFKColumn) REFERENCES dbo.YourTable(SomeUniqueColumn)
Firstly you have to make your user_id field an index: $table->index(‘user_id’); After that you can create a foreign key with an action on cascade: $table->foreign(‘user_id’)->references(‘id’)->on(‘users’)->onDelete(‘cascade’); If you want to do that with a new migration, you have to remove the index and foreign key firstly and do everything from scratch. On down() function you have … Read more
PostgreSQL automatically creates indexes on primary keys and unique constraints, but not on the referencing side of foreign key relationships. When Pg creates an implicit index it will emit a NOTICE-level message that you can see in psql and/or the system logs, so you can see when it happens. Automatically created indexes are visible in … Read more
The foreign keys will not auto-populate, as it doesn’t know what foreign key to use. You need to either insert the rows into the JobTitle_tbl table, then select the IDs back out (or use @@identity if using sql server) select id from JobTitle_tbl where Job_title=”” Another option would be to update your insert statements to … Read more
I personally stick with Database first when using EF on any schema that is this level of complexity. I have had issues with complex schemas in regards to code first. Maybe the newer versions are a little better, but worrying how to try and code complex relationships seems less straight forward then allowing the engine … Read more
I am supposing that you are talking about using the REFERENCES where the FOREIGN KEY keyword is not used when constraining a column inline, which is called a column-level foreign key constraint, eg. author_id INTEGER REFERENCES author(id) … instead of the table-level foreign key constraint, which is placed after the column declarations … author_id INTEGER, … Read more
User – Device is a many-to-many relationship, so you’ll want to introduce an intermediary table to resolve that relationship. That table simply consists of two foreign keys, one referencing the User table and one referencing Device. Device – Location can be handled with a simple foreign key in the Device table pointing to a Location … Read more
The error speaks for itself, in order to reference a composite primary key, you need a composite foreign key. (The composite primary key states that you need an unique combination of 2 fields to make a key – then you can’t possibly reference a unique key with just 1 column.) As to how this is … Read more
There is a way to bypass the validation and get it to work, thus indicating the column is a “@JoinColumnsOrFormulas” then put the solution: Error: @ManyToOne @JoinColumns(value = { @JoinColumn(name = “country_code”, referencedColumnName = “country_code”), @JoinColumn(name = “zip_code”, referencedColumnName = “code”)}) private Zip zip = null; @ManyToOne @JoinColumns(value = { @JoinColumn(name = “country_code”, referencedColumnName = … Read more
It is not possible. Relations in EF follows exactly same rules as in the database. It means that principal table must have unique identifier which is referenced by dependent table. In case of database the identifier can be either primary key or unique column(s) of principal table. Otherwise it is not valid relation. Entity framework … Read more