1 relational database
Relational database refers to a number of related tables and other database objects of a collection, this three-part definition of the meaning expressed.
a. In a relational database, information is stored in a two-dimensional sheets, a relational database contains multiple tables, each table contains rows (records) and columns (fields)
b. between tables are interrelated, this correlation is reflected in the gradual and foreign key relationships to achieve the reference
c. database includes not only tables, but also includes other database objects, such as views, indexes, stored procedures, etc.
2 key words in the database
Primary Key: The table refers to a column that uniquely identifies the value of a row, Unique & Not Null, can be formed by one or more columns
Foreign key: refers to the table with another table containing the corresponding primary key columns can be formed by one or more columns
Public key: If two tables have the same column, then the column is a public key of these two tables, if the public key is one of the table's primary key, then the public key in another table as foreign key
3. Relational database ensures data integrity and security of data storage