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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
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Python - How to Lookup Dictionary by Key

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Here's Python Dictionary that explained how to lookup it using Key. Dictionary in Python is Key/Value pair. It's different from the list. The basic rule to identify; is enclosed in flower brackets ({}). Here's a demo about lookup and how to test it. 


Dictionary = { 'key' : 'value', 'key: value'  }  


Dictionary Lookup


IN THIS PAGE

  1. Python Dictionary
  2. Python Lookup
  3. How to check Lookup working or not

Dictionary


Example

my_dict = {'name' : 'srini' , 'salary' : '100000', 'skills' : 'python' }

Here, 'name' is the label.

Then, :

Then, 'srini' -> Value

Explanation
  • Data is enclosed in flower brackets
  • It's an unordered list
  • You can manipulate data (mutable)
  • You can access the value of a particular key. So, in Python, it's called a Lookup. It's one of the best interview questions.



Lookup Dictionary by Key

Python Lookup (a.k.a Dictionary). You can access data quickly. It's really super-speed. 

my_dict['name']

The result will be: 'srini'

  • You should use square brackets ([]) to get lookup data
  • Use key-value in square brackets ([]) with a single quote, you will get value


Output from Lookup

I am now adding new value to the Lookup.

>>> my_dict['role'] = 'Manager'

Now, the my_dict will'be :

>>> my_dict = {'name' : 'srini' , 'salary' : '100000', 'skills' : 'python' , 'role' : 'Manager'}

  • The order of assignmenet will not match with actula storing in Python
  • The order of Key/Value storage is taken care by interpreter

References

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