relational model

• relational model - enable programmers to view data logically rather than physically
• table - two-dimensional structures composed of rows and columns, contains group of related entities, can be called as relation
• keys - consist one or more attributes to determine other attributes
• primary key - attribute that unique identify each entity(row), cannot be null or repeated
• foreign key - attributes whose values match primary key values in related table, can be null or repeated, control data redundancy
• candidate key - key that are potential to be primary key
• nulls - no data entry, not permitted in primary key, unknown value
• data dictionary - provides detailed accounting of all tables in database, contain all attributes name and characteristics of table, contains metadata, database designer database