VidarDB implicitly supports the primary key syntax in SQL. The first attribute in the created table is forced as the primary key in VidarDB, so the value of this attribute should be unique and not null. For example, in the following table
student, the attribute
id is used as the primary key.
CREATE FOREIGN TABLE student( id INTEGER, name TEXT ) SERVER kv_server;
If there is no proper attribute that can be used as the primary key, a table needs to add an auto-increment sequence as the first attribute. VidarDB supports the
BIGSERIAL type to create an auto-increment sequence. An example is as follows.
CREATE FOREIGN TABLE student( id SERIAL, name TEXT ) SERVER kv_server;
VidarDB supports the composite type in PostgreSQL. When a composite primary key is required, VidarDB allows multiple attributes to be combined into a composite type. The following example uses such a composite type as the primary key.
CREATE TYPE inventory_item AS ( name TEXT, supplier_id INTEGER, price NUMERIC ); CREATE FOREIGN TABLE shop ( item inventory_item, count INTEGER ) SERVER kv_server; INSERT INTO shop VALUES (('fuzzy dice', 42, 1.99), 1000);
More information about the composite type can be found in the PostgreSQL documentation