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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

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 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 placeholder '_' Perfect Way to Use it

What is placeholder in Python? The purpose of it is to mask the variable that you don't want to use in a function. In python, you can call the underscore ( _ ) operator placeholder. Below, you'll find how to use single and double placeholders in a function.


Python placeholder


What is placeholder in python

The purpose of placeholder in Python is to mask variables that you don't want to use in a function. So that your code will be readable. Moreover, in future, if you want to use those variables you can replace the placeholders with the names you want.

In This Page

You'll know in three steps how to use placeholder correctly.
  1. Creating a function
  2. Logic to use single placeholder
  3. Logic to use two placeholders

1. Creating a function.


def function_that_returns_multiple_values(x): 
      return x*2, x*3, x+1 
      for i in range(0,5): 
           square, cube, added_one = function_that_returns_multiple_values(i) 
           print(square, cube)

Here, in print, it returns two variables. I will show you how to mask the unused third variable [added_one] in the below example.

2. Logic to use single placeholder


def function_that_returns_multiple_values(x): 
      return x*2, x*3, x+1 
      for i in range(0,5): 
            square, cube, _ = function_that_returns_multiple_values(i) 
            print(square, cube)

3. Logic to use two placeholders

for i in range(0,5): 
     square, _, _ = function_that_returns_multiple_values(i)


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