There’s more than one way to do this in PostgreSQL. Personally, I prefer this way. — This table should contain all the columns common to both — audio books and printed books. create table books ( isbn char(13) primary key, title varchar(100) not null, book_type char(1) not null default ‘p’ check(book_type in (‘a’, ‘p’)), — … Read more
Foreign keys enforce referential integrity. These constraints guarantee that a row in a table order_details with a field order_id referencing an orders table will never have an order_id value that doesn’t exist in the orders table. Foreign keys aren’t required to have a working relational database (in fact MySQL’s default storage engine doesn’t support FKs), … Read more
The reason foreign key constraints exist is to guarantee that the referenced rows exist. “The foreign key identifies a column or a set of columns in one table that refers to a column or set of columns in another table. The values in one row of the referencing columns must occur in a single row … Read more
You have to define your TASK_CAT column first and then set foreign key on it. private static final String TASK_TABLE_CREATE = “create table ” + TASK_TABLE + ” (” + TASK_ID + ” integer primary key autoincrement, ” + TASK_TITLE + ” text not null, ” + TASK_NOTES + ” text not null, ” + … Read more
Simple as that, adding the WineSerializer as a field solved it. class BottleSerializer(serializers.HyperlinkedModelSerializer): wine = WineSerializer(source=”wine”) class Meta: model = Bottle fields = (‘url’, ‘wine’, ‘user’, ‘date_rated’, ‘rating’, ‘comment’, ‘get_more’) with: class WineSerializer(serializers.HyperlinkedModelSerializer): class Meta: model = Wine fields = (‘id’, ‘url’, ‘color’, ‘country’, ‘region’, ‘appellation’) Thanks for the help @mariodev 🙂
Yes, there is a way to add Primary & Foreign Keys in pgAdmin. Tested in pgAdmin III Ver.1.16.1 (Windows 7) Select the table you want Ctrl+Alt+Enter or right-click / Properties Select “Constraints” tab At the left-bottom side of the form you will see the option “Primary Key” Click add Select “Columns” tab Select the column … Read more
ssh-keygen -R hostname This deletes the offending key from the known_hosts The man page entry reads: -R hostname Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts (see the -H option above).
The Rails default behaviour is that the column used to hold the foreign key on a model is the name of the association with the suffix _id added. The :foreign_key option lets you set the name of the foreign key directly. The associations between your Post and Comment model classes should look like this: class … Read more
You can use the INFORMATION_SCHEMA tables for this. For example, the INFORMATION_SCHEMA TABLE_CONSTRAINTS table. Something like this should do it: select * from INFORMATION_SCHEMA.TABLE_CONSTRAINTS where CONSTRAINT_TYPE = ‘FOREIGN KEY’
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