Questions

Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as Primary Key. 

Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.

• One needs to be very careful in selecting the Primary Key as an incorrect selection can adversely impact the database architect and future normalization. For a Candidate Key to qualify as a Primary Key, it should be Non-NULL and unique in any domain.

Grand Central Terminal, Chicago(USA).

In the first figure, number of triangles are 5.

In the second, the figure becomes double then the number of triangles also doubles.

i.e, 10. 

Representative money is an item such as a token or piece of paper that has no intrinsic value but can be exchanged on demand for a commodity that does have intrinsic value, such as gold, silver, copper,...

Hence, a Check is an example of representative money.

• Cactus spines are also known as modified bud scales, which are also called modified leaves.

• Cactus spines occur in clusters in the axil of leaves.