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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

How to Decode Python Exception Messages Like a Pro

While developing python programs, you might see exception messages from python. Here's an explanation to understand each part of the message.


Here're tips on how to understand python exceptions. You can find two kinds of exceptions. These are StandardError and StopIteration errors. Here is a chart that shows the types of python errors.



Exception message


Python exceptions class


Execptions

Python exceptions are basically three parts. Reading an error message produced by Python is not very difficult. The error type, the error description, and the traceback.


Understand the python exception message


The Error Type

There are so many in-built exception types in python. Here is the command to get all the exception types:


[x for x in dir(__builtins__) if 'Error' in x]


The Error description

The text message right after the error type gives us a description of what exactly the problem was. These descriptions are sometimes very accurate, sometimes not.

Sample error

Traceback (most recent call last): 
    File "load_tiles.py", line 32, in <module> wall = tiles['#'] 
KeyError: '#'

After the error type, there is only a # symbol, which means no clue even for Python.

The Traceback

The traceback contains accurate information where in the code an Exception happened. It contains the following:

  • A copy of the code is executed. Sometimes we spot the defect here immediately. Not this time.
  • The line number was executed when the error occurred. The defect must be in the line itself or in a line executed earlier.

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