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Oracle


Storage can hold multiple databases
Databases can be opened by multiple instances
Server can run run multiple instances
A server can only run a single instace for any given database
Data is stored in tablespaces
A tablespace may be made up of multiple data files
Tables/indexes/Materialized Views can be partitioned across multiple segments
A segment lives on a tablespace
A database object (table, index, stored program unit...) is owned by a user
A table may be be referenced (through a foreign key constraint) by another table, including a table owned by another user
A table may have at most one primary key constraint
A table may have zero or more unique constraints
A primary key or unique constraint is logically enforced by exactly one index (though you could have a multi-column unique constraint which is backed up by multiple unique indexes with the columns in a differing order)
An index may be unique or non-unique. A unique constraint may be enforced by a unique or non-unique index.
A table must have at least one column
Each column has a datatype (and optionally a length or precision/scale)
A trigger may relate to at most a single table. (Some triggers, such as SERVERERROR, don't relate to a table).