Keys difference in dbms

#1

what is the difference between super key and primary key?

#2

hello @kani001

super key -> a set of attributes that uniquely determine tuple/row of a table/relation

primary key -> a minimal set of attributes that uniquely determine tuple/row of a table/relation.

minimal attributes means all attributes are mandatory to determine row uniquely (this condition is not there in case of super key).

u can say that primary key is subset of super key .

check this diagram ->
image

#3

minimal attributes means all attributes are mandatory to determine row uniquely (this condition is not there in case of super key). i cant understand this line can you please elaborate.minimal means all attributes are not mandatory right to uniquely identify the row?

#4

let say { A,B} is primary key .
then by minimal i mean u cant break this set furthur into smaller set to get another primary i.e alone A or alone B cannot uniquely determine a tuple (subset of primary key cannot be a primary key ).

but this is not true for super key.

#5

is primary key and candidate key same then?\

#6

yeah they are same.

we pick one key among all available candiate key and then name it as primary key.

so u can say all primary key are candiate key.