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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

 Here are the five top commonly asked SQL queries in the interviews. These you can expect in Data Analyst, or, Data Engineer interviews. Top SQL Queries for Interviews 01. Joins The commonly asked question pertains to providing two tables, determining the number of rows that will return on various join types, and the resultant. Table1 -------- id ---- 1 1 2 3 Table2 -------- id ---- 1 3 1 NULL Output ------- Inner join --------------- 5 rows will return The result will be: =============== 1  1 1   1 1   1 1    1 3    3 02. Substring and Concat Here, we need to write an SQL query to make the upper case of the first letter and the small case of the remaining letter. Table1 ------ ename ===== raJu venKat kRIshna Solution: ========== SELECT CONCAT(UPPER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, 2))) AS capitalized_name FROM Table1; 03. Case statement SQL Query ========= SELECT Code1, Code2,      CASE         WHEN Code1 = 'A' AND Code2 = 'AA' THEN "A" | "A

Python Interface Vs. Class: What's the Difference

Here are the differences between Class and Interface in Python.

Python interface

Python class can have all concrete methods. But interface does not have single concrete method.

Here you'll know about

  • What's abstract method
  • Abstract Class: How to Create it
  • Rules to Write an Interface
  • How to Create Abstract Class
  • How to Create an Interface

What's abstract method

The abstrcat method is one which does not have body.

from abc import ABC, abstract method
class name_class(ABC): # abstract class

def name_method(self): #abstract method without body

The interface is used when all the features are needed to be implemented differently for different objects.

Rules to Write an Interface

  1. All methods of an interface should be abstract.
  2. You cannot create an interface object.
  3. If any class implements an interface, then you need to define all the methods given in that interface in child class.
  4. You need to declare all methods as abstract if that class does not implement the interface

How to Create Abstract Class

from abc import ABC, abstractmethod
class Myengineer(ABC):
def mybranch(self):
myobj = Myengineer()


TypeError: Can’t instantiate abstract class Myengineer
with abstract methods mybranch

How to Create an Interface

You cannot create an object from an abstract class. But you can do it by creating a child class.

from abc import ABC, abstractmethod

#Abstract class

class Myengineer(ABC):
def mybranch(self):

#Child class implements abstract class

class MyEEE(Myengineer):
def mybranch(self):
print(“I am an electrical and electronics Engineer”)
myobj = MyEEE()


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