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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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How to Explain String Immutability in Python Correctly

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Here is an answer to explain the immutability of Strings in Python. It means that you can't modify the string. Due to this, you can use strings securely in many places of your project.


Strings Immutability


How to check string immutability

Here is an example. In the python shell, assign a value of your choice to a string. Here my choice is ABCD, and I have assigned it to myString. I have tried to replace A with Z. But, it gave an error due to the immutability of strings.


>>> myString = 'ABCD'
>>>myString [0] = 'Z'


What is learning here

The strings immutability is an interview question. In interviews, you can say that strings are immutable, and you can't replace its data.

Benefits of strings immutability

  1. It saves a lot of time since the data in strings are immutable. It results in high performance.
  2. String objects you can reuse as no one can modify its value.
  3. Strings are elemental. So no activity can change its value ( these are more like numbers).

References

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