What is a database server? Define following:
a) Primary Key
b) Foreign Key
c) Candidate key
d) Alternate key
Answers
primary key -
What is a Primary Key?
A column or group of columns in a table which helps us to uniquely identifies every row in that table is called a primary key. This DBMS can't be a duplicate. The same value can't appear more than once in the table.
Foriegn key - A foreign key is a column which is added to create a relationship with another table. Foreign keys help us to maintain data integrity and also allows navigation between two different instances of an entity. Every relationship in the model needs to be supported by a foreign key.
candidate key - A super key with no repeated attribute is called candidate key.The Primary key should be selected from the candidate keys. Every table must have at least a single candidate key.
Alternate Key -
Answer:
– Database servers are dedicated computers that hold the actual databases and run only the DBMS and related software.
PRIMARY KEY:- A primary key is a unique value that identifies a row in a table. These keys are also indexed in the database, making it faster for the database to search a record.
FOREIGN KEY:- The foreign key identifies a column or set of columns in one (referencing) table that refers to a column or set of columns in another (referenced) table.
Candidate Key: The minimal set of attribute which can uniquely identify a tuple is known as candidate key.
An alternate key is a key associated with one or more columns whose values uniquely identify every row in the table, but which is not the primary key.