Question Discussion & Solution

Concept:

A functional dependency is a constraint between two sets of attributes from the database.

Explanation:

In general form, a functional dependency denoted by X -> Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuples that can form a relation state r of R.

The constraint is that for any two tuples T₁ and T₂ in r that have T₁[X] = T₂[Y], they must also have T₁[Y]

= T₂[Y]. It means that values of Y component of a tuple in r depend on or are determined by the value of X component.

If a relation R contains attributes (X and Y). Then X -> Y is a functional dependency. It means X functionally determines Y in R if and only if two tuples agree on their X value, they must necessarily agree on their Y value.

The correct answer is Desktop.

• The first screen which appears when windows are loaded is called Desktop.

Key Points 

• Desktop
  • The first screen which appears when windows are loaded is called Desktop.
  • As soon as we open the computer we come across the Windows welcome screen which displays many small pictures on the screen of the monitor.
    • This screen is known as the desktop.
  • The small pictures on the screen are known as icons.

Additional Information

• File Folder
  • ​A file is the common storage unit in a computer, and all programs and data are "written" into a file and "read" from a file.
  • A folder holds one or more files, and a folder can be empty until it is filled. 
• Recycling Bin
  • ​A recycling bin (or recycle bin) is a container used to hold recyclables before they are taken to recycling centers. 
  • Recycling bins exist in various sizes for use inside and outside homes, offices, and large public facilities.
• Recently Added Screen
  • ​A typical “Recently Added” section looks like at the top of the Start menu app list.
  • It's a small area that shows the names and icons of recently installed apps.

The correct answer is Open Cast Mining.

• Open Cast Mining is the process under which minerals are mined near the earth's surface.

Key Points

• Opencast mining is the process that involves the removal of ore from seams relatively near the surface by means of an open-pit.
• These mines occupy a large area of land for excavation of the ore and disposal of the overburden.

Additional Information

• Drilling is a cutting process which uses a drill bit to cut a hole of circular cross-section in solid materials or ground.
• Quarrying is the process of removing rock, sand, gravel or minerals from the ground in order to use them to produce materials for construction or other uses.
• Shaft mining is the process where miners dig straight down until they reach their desired depth. 

The correct answer is Sulphur.

• The sulphur is the eye irritating compound that is released when cutting onions.
• The syn-Propanethial-S-oxide is the chemical irritant produced by an onion.
• This chemical stimulates the eyes' lachrymal glands which release tears.
• Previously scientists used to blame enzyme alinase for the instability of substances in a cut onion.
• In 2002, a study in Japan proved that lachrymatory factor synthase is responsible for irritation of the eyes.

Concept:

The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country".

The GROUP BY statement is often used with aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the result-set by one or more columns.

GROUP BY Syntax

SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
ORDER BY column_name(s);

The ORDER BY keyword is used to sort the result-set in ascending or descending order.

The ORDER BY keyword sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword.

ORDER BY Syntax

SELECT column1, column2, ...
FROM table_name
ORDER BY column1, column2, ... ASC|DESC;