what are the joins,primary key,foriegn key, candidate key,
super key and expain them?
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Answer Posted / monal
Joins: Joins are used to retrieve data from two or more
tables when there is either matching row exist in another
table or not.
Primary Key: Primary key ensures uniqueness of data in a
table so that no two rows in the table can have same value.
Foreign Key: Foreign key ensures that data entered in a
column must be checked with data already entered in the
primary key column of another table.
Candidate Key: In some tables there is possibility that more
than one column can carry unique values to make sure
uniqueness of data all across the table. one of those key
column becomes Primary key and other column become candidate
key.
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