One of the most important tasks when working with SQL is to generate Queries and retrieve data. A Query is a command given to get a desired result from the database table. The SELECT command is used to query or retrieve data from a table in the database. It is used to retrieve a subset of records from one or more tables. The SELECT command can be used in various forms:
Syntax of SELECT command:
SELECT < column-list > FROM < table-name > ;
(i) Table-name is the name of the table from which the information is retrieved.
(ii) Column-list includes one or more columns from which data is retrieved.

(i) It should identify the type of data division such as data item, segment, record and database file.
(ii) It gives a unique name to each data item type, record type, file type and data base.
(iii) It should specify the proper data type.
(iv) It should define the size of the data item.
(v) It may define the range of values that a data item may use.
(vi) It may specify privacy locks for preventing unauthorized data entry.

str1 = input ("Enter a string:")
Index=-1
while index >= -(lentstrl1)):
print ("Subscript[",index,"] :" + str1 [index])
index +=-1
Output:
Enter a string: welcome
Subscript [ -1 ] : e
Subscript [ -2 ] : m
Subscript [ -3 ] : 0
Subscript [ -4 ] : c
Subscript [ -5 ] : I
Subscript [ -6 ] : e
Subscript [ -7 ] : w

(i) Hierarchical model was developed by IBM as Information Management System.
(ii) In Hierarchical model, data is represented as a simple tree like structure form. This model represents a one-to-many relationship ie parent-child relationship.
(iii) One child can have only one parent but one parent can have many children. This model is mainly used in IBM Main Frame computers.

Advantages of DBMS:
(i) Segregation of application program
(ii) Minimal data duplication or Data Redundancy
(iii) Easy retrieval of data using the Query Language
(iv) Reduced development time and maintenance

# Python code to demonstrate table creation and insertions with SQL
# importing module
import sqlite3
# connecting to the database
connection = sqlite3.connect ("Academy.db")
# cursor
cursor = connection.cursor ( )

(i) "Required Arguments" are the arguments passed to a function in correct positional order. Here, the number of arguments in the function call should match exactly with the function definition.
(ii) Atleast one parameter to prevent syntax errors to get the required output.
(iii) Example:
def printstring(str):
print ("Example - Required arguments")
print (str)
return
# Now you can call printstring() function
printstring ("Welcome")
Output:
Example - Required arguments
Welcome

(i) We can import the definitions inside a module to another module. We use the import keyword to do this.
(ii) Using the module name we can access the functions defined inside the module. The dot (.) operator is used to access the functions. The syntax for accessing the functions from the module is.
<module name>. <function name>
(iii) Example: >>> factorial.fact(5)

class Sample:
def _init_(self, n1, n2):
self.n1=n1
self._n2=n2
def display(self):
print("Class variable 1 = ", self.n1)
print("Class variable 2 = ", self._n2)
S=Sample(12,14)
S.display()
print("Value 1 = ", S.n1)
print("Value 2 = ". S._n2)
Reason: The print statements defined within class will successfully display the values of n1 and n2, even though the class variable n2 is private because, in this case, n2 is called by a method defined inside the class. But, when we try to access the value of n2 from outside the class Python throws an error because, private variable cannot be accessed from outside the class.

(i) Object is a collection of data and function that act on those data. Class is a template for the object
(ii) According to the concept of Object Oriented Programming, objects are also called as instances of a class or class variable.
(iii) In Python, everything is an object. For example, all integer variables that we use in our program is an object of class into Similarly all string variables are also object of class string.

#importing csv
import csv
#opening the csv file which is in different location with read mode
with open('c:\\pyprg\\ sample1.csv', 'r') as F:
#other way to open the file is f= ('c:\\pyprg\\ sample1.csv', 'r')
reader = csv.reader(F)
# printing each line of the Data row by row
print(row)
F.close ( )

(i) A set is created by placing all the elements separated by comma within a pair of curly brackets. The set( ) function can also used to create sets in Python.
(ii) Syntax:
See Variable = {E1, E2, E3 .......... En}
(iii) Example:
> > > S1 = {1, 2, 3, 'A', 3.14}
> > > print(S1)
{1, 2, 3, 3.14, 'A'}
> > > S2={1, 2, 2, 'A', 3.14}
> > > print(S2)
{1, 2, 'A', 3.14}
In above examples, the set S1 is created with different types of elements without duplicate values. Whereas in the set S2 is created with duplicate values, but Python accepts only one element among the duplications, which means python removed the duplicate value because a set in Python cannot have duplicate elements.

Output:
(i) 2
(ii) 1
(iii) [12, 12, 36]

MyList = [2, 4, 5, 8, 10]
print ("MyList elements before update ... ")
for x in MyList:
print (x)
MyList[2] = 6
print ("MyList elements after updation ... ")
for y in MyList:
print (y)
Output:
MyList elements before update ...
2
4
5
8
10
MyList elements after updation ...
2
4
6
8
10

(i) The len( ) function in Python is used to find the length of a list. (i.e., the number of elements in a list).
(ii) Usually, the len( ) function is used to set the upper limit in a loop to read all the elements of a list.
(iii) If a list contains another list as an element, len( ) returns that inner list as a single element.
(iv) Example: Accessing single element
> > > MySubject = ['Tamil', 'English', 'Comp', 'Science', 'Maths']
> > > len(MySubject)
4

(i) Start with the first element i.e., index = 0, compare the current element with the next element of the array.
(ii) If the current element is greater than the next element of the array, swap them.
(iii) If the current element is less than the next or right side of the element, move to the next element. Go to Step 1 and repeat until end of the index is reached.

(i) Hexadecimal literal
(ii) Complex literal
(iii) Floating point literal
(iv) Octal literal

x = int(input ("Enter Number 1")
y = int(input("Enter Number 2")
print ("The sum of", x, " and ", y, "is", x+y)

(1) input
(2) Chennai
(3) City

(i) Public members (generally methods declared in a class) are accessible from outside the class.
(ii) Protected members of a class are accessible from within the class and are also available to its sub-classes.
(iii) Private members of a class are denied access from outside the class. They can be handled only from within the class.

(i) Data abstraction is supported by defining an abstract data type (ADT) which is a collection of constructors and selectors.
(ii) Constructors create an object, bundling together different pieces of information, while selectors extract individual pieces of information from the object.

(i) The syntax to define functions is close to the mathematical usage: the definition is introduced by the keyword let, followed by the name of the function and its arguments; then the formula that computes the image of the argument is written after an = sign. If you want to define a recursive function: use "let rec" instead of "let".
(ii) Syntax: The syntax for function definitions:
let rec fn a1 a2 ... an :;= k
(iii) Here the 'fn' is a variable indicating an identifier being used as a function name. The names 'a1' to 'an' are variables indicating the identifiers used as parameters. The keyword 'rec' is required if 'fn' is to be a recursive function; otherwise it may be omitted.