1. The relational database is the application of mathematical methods to process the data. It has a knot
configuration is simple, solid theoretical basis, provide high data independence and non-procedural
language and so on.
A set of values: 2. domain (Domain). They have the same data type
, Usually in the range of a semantic object.
For example: all integers
between integer of 0 to 100,
no longer than the set of strings 10
3. The Cartesian product (Cartesian Product): set D1, D2, ..., Dn
is n domain, their Cartesian product is
D1 * D2 * ... * Dn = {(d1, d2, ..., dn) | di belonging to di, i = 1,2, ..., n}
where each element is called an n-tuple (n-tuple), referred to as a tuple;
each value of di is called a tuple component (component).
4. Relationship Model
Three parts: the relationship between the data structure, the operation set relationship, the relationship between the integrity of the
The key may have a plurality of, collectively candidate key. In use, through
Often chosen as a primary key. Various primary key attribute is called primary metal
properties, other non-primary property.
6. Three types of relationships
Fundamental relationship: an objective base table
lookup table: a basic table retrieved under certain conditions result
View (View): the relationship derived from one or more fundamental relationship. It
does not correspond to the actual stored data, it is a virtual relationship, however, may be permanently present.
Equivalent model outside the relational model.
7. storing operation
(1) Modify: UPDATE
(2) is inserted: PUT
(3) Delete: DELETE
keyword can not be modified,
only to delete, and then insert