DB2 for z/OS
DB2 UDB is a relational database management system that enables users to create, update and control relational databases using SQL.
SQL(Structured Query Language) is a standardized language for defining and manipulating data in a relational database.
Tables: are logical structures maintained by DB2 made up of columns and rows.
Index: an index is an ordered set of points to rows of a base or an awxiliary table.
Key: a key is one or more columns that are indentified as such in the description of a table, an index or a referential constraint.
Unique key: a key that constrained so that no two of its value are eaqul.
Primary key: is an unique key that is a part of definition of a table. A table can only have one primary key, and the columns of a primary key cannot contain null values.
Parent key: is either a primary key or an unique key in the parent table of a referrntial constraint, the values of a parent key determine the valid values of the foreign key in the constraint.
Foreign key: is a key that is specified in the definition of a referential constraint, refers to or related to a specific parent key. A table can have zero or more foreign keys.
