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.

The logical answer for a puzzle is that the letter 'W'.

A rainbow is a spectrum of light that appears in the sky when sunlight is refracted through raindrops or other drops of moisture in the Earth's atmosphere. They have inspired much popular folklore, including the belief that a leprechaun can be found with a pot of gold at the end of a rainbow.

Bengaluru has became the second city in the country, and the first in south India, to have a full-fledged Metro rail in operation following the opening of a final 12-km section of the 42-km first phase of the Metro project. The first phase, comprising an 18-km east-west line and a 24-km north-south line, built at a cost of Rs 13,845 crore, was dedicated to the nation by President Pranab Mukherjee at an event in Bengaluru.

Concatenation of text means adding a word with other word. It can be done using Ampersand (&).

For example :

'Amper' & 'sand' = Ampersand