Question

difference between primary key ,candidate key,foreign key , alternative key​

Answer 1

Answer:

primary key : uniquely identifies a column in table

candidate key : key which is eligible to become primary after existing primary key

alternative key : key which may me used instead of existing key

foreign key : uniquely identifies a column blw two tables

Answer 2

Answer:

Helps you to uniquely identify a record in the table. It is a field in the table that is the primary key of another table. Primary Key never accept null values.

A foreign key may accept multiple null values.

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. For example, where the primary key for a table may be the employee id, the alternate key might combine the first, middle, and last names of the employee.D